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Unit 3: Genetics.

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1 Unit 3: Genetics

2 a. Explain the concept of independent events.
1. Explain the significance of Mendel`s experiments and observations and the laws derived from them. a. Explain the concept of independent events. b. Understand that the probability of an independent event is not altered by the outcomes of previous events.

3 Heredity All organisms pass on their characteristics from generation to generation through INHERITANCE. 2 kinds of characteristics inherited: Species characteristics: each species always passes on their own traits. Individual Characteristics: even though we inherit things equally from both parents, offspring is always different from their parents because we are a combination of both parents (i.e. mother's hair colour, father's build, mother's nose, etc.) Heredity is controlled by a chemical code in our DNA. This genetic code is present in the chromosomes of the gametes (egg and sperm).

4 Environment Independent Events
Even though we inherit traits from our parents, our environment will affect the full potential of what we inherit. Example: Food: people in Canada are bigger and taller than 100 years ago Exercise: stronger, healthier bodies Sunlight: lightens hair, darkens freckles Independent Events Another factor that will affect what we inherit are independent events. An event that takes place that no previous event has an effect on. Example: you broke your finger when you were six and it is now crooked. You will not pass this crooked finger on to any of your offspring, it is an independent event.

5 Probability In genetics, we use a mathematical process called probability. Probability is the chance that an event will occur (i.e. the chance that you will have curly hair or blue eyes). When determining probability, we do not consider items like the environment or independent events.

6 In-Class Discussion How does heredity affect you?
What traits have you received that are NOT affected by the environment or independent events? What traits have you received that have been affected by the environment or independent events Instructions: 1. In groups of 2 or 3, discuss the 3 questions above, make a list of traits that have been inherited, and a list of traits that have been affected/altered. 2. Look at the list of traits that your group has made and decide which ones are most common and which ones are not as common....decide what this might have to do with the terms "dominant" and "recessive".

7 List of Traits: Dominant or Recessive:

8 Dominant and Recessive Genes
Dominant Gene: determine the expression of the genetic trait in offspring. Dominant gene is given an upper case (capital) letter. Recessive Gene: genes that are overruled by dominant genes. Recessive gene is designated by a lower case letter. Other Examples: To determine some other examples of traits that are dominant or recessive, we will conduct a class survey.

9 1. What does the term "heredity" mean?
Review... 1. What does the term "heredity" mean? 2. What is the difference between a dominant and a recessive trait? Provide an example of each.

10 1. Explain the significance of Mendel`s experiments and observations and the laws derived from them.
c. Describe Mendel`s experiments and observations. d. Describe the relationship between genotype and phenotype. e. Use the concept of the gene to explain Mendel`s Laws. f. Describe the ideas of dominant and recessive traits with examples. h. Explain the law of segregation.

11 GENETICS GENETICS: the branch of biology that studies the ways in which 
hereditary information is passed on from parents to offspring. GREGOR MENDEL: ( ) first to study heredity (monk). studied pea plants (traits) and came up with some basic principles. Peas: easy to grow, mature quickly, show sharply contrasting traits 
(tall vs. short, yellow vs. green, wrinkled vs. smooth). Easy to cross pollinate for humans. Kept careful records.

12 Mendel and His Experiments
Gregor Mendel:  Austrian monk  studied garden peas Mendel studied peas and cross-fertilized them by hand. Peas had specific 
traits that he studied. Crosses:  Round seeds X Wrinkled (parents)   Round Seeds (offspring)  Tall plants X Short plants (parents)   Tall Plants (offspring) Yellow seed coats X Green seed coats (parents)   Yellow seed coats (offspring)

13 Mendel discovered that genes control the traits of a plant
Mendel discovered that genes control the traits of a plant. Genes are located 
on chromosomes. Mendel also discovered that some genes are dominant over others 
(recessive). Ex)  round seeds dominant over wrinkled seed  tall plants dominant over short plants  yellow seed coat dominant over green seed coats Dominant Gene: determine the expression of the genetic trait in offspring. Dominant gene is given an upper case (capital) letter. Recessive Gene: genes that are overruled by dominant genes. Recessive gene is designated by a lower case letter. For each trait, an organism gets one gene form the mother and one gene 
from the father.

14 Mendel's Laws of Heredity:
1. Inherited characteristics are controlled by genes. Genes happen in pairs. During fertilization 2 genes come together to form a pair. 2. Principle of Dominance one gene masks the effect of another. The gene for round seed coats masks the effect of the gene for wrinkled seed 
coats. Round is dominant over wrinkled. 3. Law of Segregation: Genes separate during the formation of sex cells. Organisms get one gene from each parent for a particular trait. During the 
formation of gametes (sex cells), alleles (form of a gene) separate randomly 
so that each gamete receives one or the other. The Law of Segregation 
deals with meiosis, which will be talked about later.

15 Genotype: refers to the genes that an organism has for a particular trait. Ex) RR, Rr, rr; a round seed coat can have genotype RR or Rr, a wrinkled seed coat has only one genotype rr. YOU CAN'T TELL THE GENOTYPE BY JUST LOOKING AT AN ORGANISM Phenotype: refers to the observable traits of an organism, the traits that you see, Ex) there are only 2 phenotype for seed coat, wrinkled and smooth. Homozygous: an organism contains 2 genes for one trait that are the same, Ex) RR or rr : the organism is pure for the trait. Heterozygous: an organism contains 2 genes for one trait that are different. Ex) Rr Alleles: two or more alternate forms of a gene. Ex) Dominant Recessive seed coat alleles R (smooth) r (wrinkled)

16 Review.... 1. List and explain one of the new terms learned last day. 2. What was one of Gregor Mendal's laws?

17 1. Explain the significance of Mendel`s experiments and observations and the laws derived from them.
g. Consider the value of the punnett square by creating examples of mono and dihybrid crosses.

18 Monohybrid Cross Mono (one)
Hybrid (result from crosses between parents that are genetically not 
alike) Monohybrid Cross: a cross that involved one pair of contrasting genes for 
one trait.

19 Ex) Dealing with the trait of Seed Coat
Round seed coat X Wrinkled seed coat (parent) RR rr Crossed Again (F1 generation) Hybrid Offspring X Round Seed Coat Rr Rr (F = filial) rr RR Rr Rr (F2 generation)

20 Wrinkled Parent (homozygous)
Punnet Square for Monohybrid Cross Punnet Square: chart used by geneticists to show the possible combinations of alleles in offspring. Wrinkled Parent (homozygous) r R Round Parent (homozygous) (F1 generation) all _ Rr, heterozygous

21 Round Parent (heterozygous)
(F2 generation) _ RR homozygous dominant, _ Rr heterozygous and _ rr homozygous (recessive)

22 Monohybrid Cross Phenotypic Ratio
Monohybrid Cross Genotypic Ratio 1 RR (homozygous dominant) : 2Rr (heterozygous) : 1rr (homozygous recessive) Monohybrid Cross Phenotypic Ratio 3 round : 1 wrinkled 3 with the dominant trait showing : 1 with the recessive trait showing 3/4 or 75% : 1/4 or 25%

23 Lets look at this in more detail.
RR X rr (parents) sex cells r r R R Rr (F1 generation) R r (F2 generation) round wrinkled

24 Examples: 1. Brown eyes (B) are dominant over blue eyes. If a parent homozygous for blue eyes produce offspring. What are the chances that the offspring has brown eyes? blue eyes? Parent A = BB Parent B = bb

25 2. In plants, tall (T) is dominant over short (t)
2. In plants, tall (T) is dominant over short (t). Two plants, that are tall, are crossed and produce a plant that is short. Determine the genotype of the parents. short plant = tt

26 3. In guinea pigs, curly hair (C) is dominant over straight hair (c)
3. In guinea pigs, curly hair (C) is dominant over straight hair (c). If two guinea pigs that have curly hair and are straight hair carriers mate, what is the chance they have a straight haired offspring? Genotype of parents =

27 1. Explain the significance of Mendel`s experiments and observations and the laws derived from them.
g. Consider the value of the punnett square by creating examples of mono and dihybrid crosses.

28 Review Question.... 1. Both a hen and a rooster are heterozygous trait carriers. They both have a trait to be black (B) and a trait to be white (b). Black is the dominant colour, what will the phenotypes and genotypes of their offspring be?

29 Dihybrid Cross Di = 2 Hybrid: result from crosses between parents that are genetically not alike. Dihybrid cross: a cross that involves 2 traits.

30 Yellow Round X Green Wrinkled
Example of a dihybrid cross: Yellow Round X Green Wrinkled (parent) (gametes YR) YYRR yyrr (gametes yr) Crossed Again (F1 generation) X Yellow Round YyRr YyRr (gametes = YR, Yr, yR, yr) (gametes = YR, Yr, yR, yr) (F2 generation) 1 YYRR, 2 YyRR, 2 YYRr, 4 YyRr, 1 YYRR, 2 yyRr, 1 yyrr, 1 YYrr

31 Punnet Square for Dihybrid Cross
Green and Wrinkled Parent 
(homozygous) yyrr YYRR yr yr Parent Yellow & Round (homozygous) YR YR (F1 Generation) _ YyRr (yellow & round, heterozygous)

32 Dihybrid Cross Phenotypic Ratio
YyRr Yellow & Round Parent (heterozygous) YR Yr yR yr YyRr Yellow & Round Parent (heterozygous) Dihybrid Cross Phenotypic Ratio 9/16 Yellow & Round : 3/16 Yellow & Wrinkled : 3/16 Green & Round : 1/16 Green & Wrinkled **Remember** Dihybrid Cross = 9 : 3 : 3 : 1

33 Examples.... 1. Black coat colour (B) in cocker spaniels is dominant to white coat colour (b). Solid coat pattern (S) is dominant to spotted pattern (s). A male that is black with a solid pattern mates with two females. The mating with female A which is white, solid, produces four pups: 2 black, solid, and two white, solid. The mating with female B, which is black, solid, produces a single pup, which is white, spotted. Indicate the genotypes of the parents.

34 2. In guinea pigs, black coat colour (B) is dominant to white (b), and short hair length (S) is dominant to long (s). Indicate the genotypes and phenotypes from the following crosses: a) Homozygous for black, heterozygous for short-hair guinea pig crossed with a white, long-haired guinea pig. b) Heterozygous for black and short-hair guinea pig crossed with a white, long-hair guinea pig.

35 c) Homozygous for black and long-hair crossed with a heterozygous black and short-hair guinea pig.

36 2. Discuss the relationship among chromosomes, genes, and DNA.
h. Examine incomplete dominance, alleles, sex determination, and sex-linked traits in the context of human genetics. i. Discuss several human genetic disorders such as hemophilia, sickle-cell anemia, Down`s syndrome, and Tay-Sach`s disease.

37 Test Cross There is an organism showing the dominant trait but it is unknown if the 
organism is homozygous or heterozygous, it's genotype is unknown. To figure 
out the genotype you cross the unknown genotype and a homozygous recessive 
genotype. If the offspring all show the dominant trait, the unknown genotype is 
homozygous dominant. If any of the offspring show the recessive trait, the unknown genotype was 
heterozygous dominant.

38

39 Determine the genotype of the parent plants by looking at the phenotypes of the offspring from the following cross. Round, yellow X  Wrinkled, green 1/4 round, yellow, 1/4 round, green, 1/4 wrinkled, yellow, 1/4 wrinkled, green

40 Incomplete Dominance The lack of a dominant gene. Both alleles contribute to the phenotype of a 
heterozygote. Produces an offspring with traits unlike either parent. Ex) Red snapdragon (RR) X White snapdragon (WW) F1Generation All Pink Snapdragons (RW) RW X RW F2 Generation  R W R W 1 RR (red) : 2RW (pink) : 1 WW (white)

41 Codominance Two dominant genes are expressed at the same time in the heterozygous 
organism. Ex) Shorthorn Cattle Red (HRHR) X White (HWHW) Roan Calf - it has intermingling of white and red hair F1 Generation (all) HRHW X HRHW F2 Generation HR  Hw HR HW 1 HRHR : 2HRHW : 1HWHW

42 Multiple Alleles The problem we have dealt with so far only have dealt with 2 alleles - the 
dominant allele and the recessive allele. The dominant allele controlled 
the trait. Multiple Alleles - when more than 2 different alleles exist for a trait. Ex) the fruit fly Drosophilz - many different eye colors are possible.  Red (wild type) eyes : most common  Apricot  Honey  White Dominant Hierarchy Note: a drosophila can only have 2 different genes at one time, but many alleles 
are possible.

43 When using multiple alleles we no longer use upper and lower case 
letters. Capital letters with subscript numbers are used. Red (wild type) eyes E1E1 OR E1E2, E1E3, E1E4 Apricot E2E2, E2E3, E2E4 Honey E3E3, E3E4 White E4E4

44 Ex) Human Blood Typing: example of codominance and multiple alleles
The ABO blood typing system in humans is determined by a set of 3 alleles 
- multiple alleles. IA, IB, i Different combinations of these alleles in people produce 4 different blood 
types.  Type A, Type B, Type AB, Type O Genotype Phenotype IAIA or IAi Type A Blood IBIB or IBi Type B Blood IAI B Type AB Blood * ii Type O Blood * This is codominance - different alleles expressing their full phenotype in a 
heterozygote, giving a new phenotype.

45 Exceptions to Mendel's Laws Example Questions...
1. For ABO blood groups, the A and B genes are codominant, but both 
A and B are dominant over type O. Indicate the blood types possible 
from the mating of a male who is blood type O with a female of blood 
type AB. 2. Could a female with blood type AB ever produce a child with blood 
type AB? Could she ever have a child with blood type O?

46 Exceptions to Mendel's Laws Example Questions...
3. Thalassemia is a serious human genetic disorder that 
causes severe anemia. The homozygous condition (TmTm) leads to sever anemia. People with thalassemia die before sexual 
maturity. The heterozygous condition (TmTn) causes a less serious form of anemia. The genotype TnTn causes no symptoms of the disease. Indicate the possible genotypes and 
phenotypes of the offspring if a male with the genotype TmTn marries a female of the same genotype.

47 Review... 1. What is incomplete dominance? Provide an 
example. 2. What is meant by the term "multiple alleles?" 
Provide an example. 3. What is co-dominance?

48 2. Discuss the relationship among chromosomes, genes, and DNA.
h. Examine incomplete dominance, alleles, sex determination, and sex-linked traits in the context of human genetics. i. Discuss several human genetic disorders such as hemophilia, sickle-cell anemia, Down`s syndrome, and Tay-Sach`s disease.

49 Incomplete Dominance Examples...
A cross between a blue blahblah bird and a white blahblah bird 
produces offspring that are sliver. The color of blahblah birds 
is determined by just two alleles. a) What are the genotypes of the parent blahblah birds in the 
original cross? b) What is/are the genotyp(s) of the silver offspring? c) What would be the phenotypic ratios of offspring produced by two silver blahblah birds?

50 Incomplete Dominance Examples...
1. The color of fruit for Golgi plants is determined by two alleles. 
When two plants with orange fruits are crossed the following 
phenotypic ratios are present in the offspring: 25% red fruit, 50% 
orange fruit, 25% yellow fruit. What are the genotypes of the 
parent orange-fruited plants?

51 Co-dominance Example Problem...
1. Predict the phenotypic ratios of offspring when a 
homozygous white cow is crossed with a roan bull? 2. What should the genotypes and phenotypes for parent 
cattle be if a farmer wanted only cattle with red fur?

52 Multiple Alleles Example Problem...
1. Remembering what you learned about blood types, what are 
the possible phenotypes of children in the following families? a) Heterozygous type A mother, Homozygous type A father? b) Homozygous type B mother, type AB father? c) type AB mother, type AB father?

53 2. Discuss the relationship among chromosomes, genes, and DNA.
h. Examine incomplete dominance, alleles, sex determination, and sex-linked traits in the contexts of human genetics. i. Discuss several human genetic disorders such as hemophilia, sickle-cell anemia, Down`s syndrome, and Tay-Sach`s disease. j. Discuss the similarities and differences between sex chromosomes and somatic chromosomes.

54 Sex - Linked Traits Sex-linked traits : controlled by genes located on the sex chromosomes. In humans the sex chromosomes go as follows:  Female = XX Male = XY The X chromosomes are relatively the same size.  In a female you have two homologous X chromosomes. - - Locus: the actual site of the 
gene on a chromosome. X X

55 In a male you have one large X chromosome and a smaller Y chromosome
In a male you have one large X chromosome and a smaller Y 
chromosome. The Y chromosome is shorter than the X chromosome. 
Some of the genes on the X chromosome may be missing on the Y 
chromosome. - There is nothing to match. X Y Most sex-linked traits are determined by genes found on the X 
chromosome but not on the Y chromosome.

56

57 XX' XX X'X' Sex-linked disorders in Humans:
1. Color-Blindness: person can't perceive certain colors, usually red and green.  : more common in males than females.  : Females may be carriers for it, because they have the recessive allele 
for color-blindness on one X chromosome and the normal dominant allele on 
the other X chromosome. Female Carrier Normal Female Color-blind Female XX'  XX  X'X' 

58 Every male gets an X chromosome from its mother and a Y chromosome 
from his father.
  Mother = XX  Father = XY Male Offspring  XY Mother a Carrier  Father XX'  XY Male Offspring XY or  X'Y  There is a 50% chance that the male son will have color blindness.

59 Since the Y chromosome is smaller than the X, the Y chromosome 
has no spot for color vision. When a son gets the defective color blind 
allele from his mother the color blindness is expressed and the son is 
color blind. In order for a female to be color blind, she must inherit the color 
blind allele from both parents and this is a rare event. Mother  Father XX'  X'Y Color-Blind Female Offspring X'X' Remember: color-blindness is transmitted only through the female.

60 2. Hemophilia: sex-linked disorder in which the blood is unable to clot 
because it lacks a certain blood-clotting protein.  : the recessive gene for hemophilia is carried on the X 
chromosome.  : Most affected individuals are male.  : Females with one recessive genes are carriers but show no sign 
of the illness.  : Smallest cut or bruise can cause the person to bleed severely.

61 Pedigree - means of tracing sex-linked traits in family trees through a pictorial 
representation - females are represented by circles, males are represented as squares. - matings are shown by horizontal lines connecting two individuals - offsprings are connected by vertical lines to the mating line - different shades or colors added to the symbols represent carious phenotypes - each generation is listed on a separate row labeled with Roman Numerals

62 Pedigree

63 Review... 1. Explain why it is more likely for a male child to be 
born colorblind if his father is normal, but his 
mother is a carrier for colorblindness.

64 2. Discuss the relationship among chromosomes, genes, and DNA.
a. Describe how the genetic code is carried on the DNA. i. Discuss several human genetic disorders such as hemophilia, sickle-cell anemia, Down`s syndrome, and Tay-Sach`s disease.

65 Chromosomes Chromosomes: long threads of genetic material found in the nucleus of cells  : made up of nucleic acids and proteins  : humans have 46 chromosomes (23 pairs) Genes: located on the chromosomes  - made up of DNA  - units of instruction, located on chromosomes that produce or 
influence a specific trait in offspring. DNA-deoxyribonucleic acid: carries the genetic code, carries genetic information.

66 Diploid Chromosome Number: (2n) the full compliment of chromosomes
Diploid Chromosome Number: (2n) the full compliment of chromosomes. Everyday cells in the body, except sex cells 
have a diploid chromosome number (ex- Humans = 46) Haploid Chromosome Number: (n) one half of the full compliment of chromosomes. Sex cells have haploid chromosome number (ex- 
Humans=23) Homologous Pairs/Homologous Chromosomes: are similar in size, shape, and gene arrangement. Get one from each parent (ex - 23 pairs 
in humans).

67 Karyotype: pictures of chromosomes arranged in homologous pairs.

68 Sex Chromosomes: chromosomes that determine the sex of an individual
Sex Chromosomes: chromosomes that determine the sex of an individual. Ex) Human pair #23 XY = male XX = female Somatic Chromosome/Autosomes: chromosomes not involved with sex determination. Ex) Human pairs #'s 1-22. Monosomy: is the presence of a single chromosome in place of a homologous pair. Ex) Turner's Syndrome: a female that has a single X chromosome (pair 
#23). Only females, do not develop sexually, tend to be short and 
have thick wide necks.

69 Trisomy: the presence of three homologous chromosomes in place of homologous pair.
Ex) Down's Syndrome: an extra chromosome for pair #21. Often 
called trisomy 21. Characteristics include round full face, enlarged 
creased tongue, short height, large forehead and decreased mental 
capabilities. Ex) Klinefelter Syndrome: 3 sex chromosomes (XXY). Appears to be puberty produces large amounts of female hormones. Sterile.

70 2. Discuss the relationship among chromosomes, genes, and DNA.
b. Outline the process of replication. d. Describe the process of transcription. e. Describe the functions of mRNA, tRNA, amino acids, and ribosomes in protein synthesis.

71 Protein Synthesis 1. Transcription 2. Translation

72 2. Discuss the relationship among chromosomes, genes, and DNA.
f. Describe the causes and effects of both chromosomes and gene mutations.

73 Mutations Handout

74 2. Discuss the relationship among chromosomes, genes, and DNA.
k. Using examples from living organisms discuss the importance of asexual and sexual reproduction to their growth and survival.

75 Asexual vs. Sexual Reproduction
a. Asexual Reproduction Asexual cell division = mitosis - producing 2 daughter cells identical to 
the parent cell. Asexual reproduction in organisms involves one parent with the 
offspring looking identical to nearly identical to the parent. Cloning is a type of asexual reproduction. Budding is a type of asexual reproduction (ex. hydra, strawberries). There is no variation in traits with asexual reproduction, this is 
dangerous because what happens if there is a change in environment.

76 b. Sexual Reproduction:
Sexual cell reproduction = meiosis - producing gametes that have genetic 
variation. Animals that reproduce sexually have male and female sexes. They produce 
gametes through the process of meiosis. Humans reproduce sexually. In sexual reproduction there is diversity and genetic variation. An advantage of sexual reproduction is that there is variety in the population 
and some organisms may be better able to survive (survival of the fittest); or if 
there is an environmental change some organisms may survive while others may 
not.

77 2. Discuss the relationship among chromosomes, genes, and DNA.
c. Compare mitosis and meiosis.

78 Mitosis... The process in which the cell triggers itself to asexually reproduce forming 
2 identical daughter cells from 1 parent cell Necessary for growth and to replace injured cells Before the mother cell splits, the chromosomes in it have duplicated into 
2 sets. When the mother cell splits, 1 set of chromosomes goes to each of the 2 daughter cells. The process a cell goes through to duplicate itself is called the cell cycle, and looks like this:

79 Mitosis Cell division occurs in a series of stages, or phases.
1st INTERPHASE Chromosomes are copied (# doubles). Chromosomes appear as threadlike coils 
(chromatin) at the start, but each chromosome and its 
copy (sister chromosome) change to sister chromatids 
at end of this phase. centromere 2nd: PROPHASE Mitosis begins (cell begins to divide) Centrioles (or poles) appear and begin to move 
to opposite ends of cell. Spindle fibers form between the poles.

80 3rd: METAPHASE Chromatids (or pairs of chromosomes) attach to 
the spindle fibers. sister chromatids 4th: ANAPHASE Chromatids (or pairs of chromosomes) separate 
and begin to move to opposite ends of the cell. sister chromatids split

81 5th: TELOPHASE Two new nuclei form Chromosomes appear as chromatin (threads 
rather than rods) Mitosis ends 6th: CYTOKINESIS Cell membrane moves inward to create two 
daughter cells - each with its own nucleus with 
identical chromosomes.

82 One final note... - During telophase in plant cells, a cell plate forms in the center and grows outward creating a cell wall (rather than the cell membrane 
pinching inward). cell plate

83 Review... 1. What happens, most importantly, during 
interphase? 2. What is the end result of mitosis?

84 2. Discuss the relationship among chromosomes, genes, and DNA.
c. Compare mitosis and meiosis.

85 Meiosis... Is the process that takes place in the sex organs of all living organisms in 
order to produce haploid sex cells (also known as gametes). This process is absolutely essential, otherwise at fertilization, when two 
gametes unite together, there would be too many chromosomes! In humans, meiosis reduces the number of chromosomes from 46 to 23, 
so that every sperm or egg cell has 23 chromosomes. At fertilization, 23 
chromosomes from the sperm unite with 23 chromosomes from the egg to 
produce the original 46 chromosomes.

86 Meiosis: two divisions of chromosomes
a. MEIOSIS I = first round of divisions; stage where the chromosome # is 
reduced by half i) INTERPHASE I: as in interphase of mitosis, it is the period during which the 
cell grows and replicates its chromosomes ii) PROPHASE I Early Prophase I: - chromosomes appear as long, thin threads - nucleoli starts to disappear and centrioles move to opposite 
ends of the cell Middle Prophase I: - the chromosomes come together in homologous pairs 
through the process of synapsis (intertwining) - each homologous pair is composed of chromatids and is 
referred to as a tetrad - intertwined chromatids may break and exchange segments = 
crossing over - tetrads become shorter and thicker Late Prophase I: - centrioles are at opposite poles - spindle formation is complete - nucleus begins to dissolve

87 - now, half the number of double stranded chromosomes at each pole
iii) METAPHASE I - each tetrad moves onto a spindle 
and attaches to a single fibril at the 
equator iv) ANAPHASE I - centromeres do not divide and 
homologous chromosomes move apart to 
opposite poles in a process called 
segregation - now, half the number of double 
stranded chromosomes at each pole

88 v) TELOPHASE I - the two sets of double stranded 
chromosomes become enclosed in new 
nuclei - chromosomes remain double stranded and 
disappear - cytokinesis occurs creating two haploid 
daughter cells that are NOT identical

89 b) MEISOSIS II: occurs in both haploid daughter cells at the same time
Interkinosis: basically interphase, except there is no replication of chromosomes i) PROPHASE II - nuclear membrane dissolves - centrioles move and spindles form - double-stranded chromosomes 
shorten and thicken ii) METAPHASE II - double-stranded chromosomes 
attach the spindle and line up at the 
equator

90 - sister chromatids move to opposite poles
iii) ANAPHASE II - the centromere holding each pair of 
sister chromatids together dissolves - sister chromatids move to opposite poles iv) TELOPHASE II - nuclear membranes are restored, 
spindles disappear, and cytokinesis 
occurs - results in 4 haploid daughter cells 
that are different from each other 
and the parent cell

91 Review... 1. What is the end result of meiosis? 2. Why must our sex cells be produced through 
meiosis and not mitosis?

92 2. Discuss the relationship among chromosomes, genes, and DNA.
g. Consider the purposes and techniques of gene mapping.

93 Genetic Engineering Activities Gene Mapping
there are approximately 100 thousand genes in the nucleus of each human 
cell among the 46 chromosomes. Human Genome all the genes that make up the 'master blue print' 3 billion base pairs of nucleotide bases that make up DNA

94 Human Genome Project to identify the full set of genetic instructions contained in our cells and to 
read the complete text written in DNA. Worked on by 100's of biologists, chemists, engineers, mathematicians, 
etc. all over the world. Will revolutionize our understanding of how genes control the function of 
the human body. Provide new strategies to diagnose, treat, prevent human diseases. Estimate to take 15 years.  1) complete maps of the 46 chromosomes  2) sequence the DNA in chromosomes it's like shedding an encyclopedia and trying to put it back together again so 
it can be read. Consider: Body made of several trillion body cells. Each cell has 46 chromosomes in nucleus. Each chromosome is made of DNA with thousands genes. 3 billion base pairs make of DNA.

95 3. Delineate the impact of biotechnology on our society.
a. Describe the basic processes involved in the production of recombinant DNA. b. Discuss examples of current uses of recombinant DNA technology in the agricultural and pharmaceutical industries. c. Discuss techniques of genetic screening. d. Consider the implications of genetic screening of adults, children, and fetuses.

96 Research Project

97 a. Describe the concepts of the deme and gene pool.
4. Discuss the application of population genetics to the study of evolution. a. Describe the concepts of the deme and gene pool. b. Consider the Hardy-Weinberg principle. c. Describe the factors which influence genetic drift. d. Consider the relevance of the gene pool and the idea of mutations to the concept of evolution.

98 Population Genetics Activities


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