1. Chapter 10 Sexual Reproduction and Genetics

2. Two of these people are genetically related, can you tell which two?

3. Section 10.1 - Meiosis Main Idea : Meiosis produces haploid gamates.
Meiosis is a type of cell division that reduces the number of chromosomes.
46 pairs reduced to 23 pairs
A cell with half the number of chromosomes is called haploid. (23 chromosomes n)
This type of cell division is important in the life cycle of organisms such as animals.

4. Why is meiosis cell division important?
Human body cells have 46 chromosomes.
Each parent gives half of their chromosomes (23) to their offspring.
The chromosomes that make up a
pair, one chromosome from each
parent is called a
homologous chromosome.

5. Passing on genetic traits
Each chromosome
consists of hundreds of
genes.
Genes are DNA
segments that carry
instructions for inherited
traits such as eye color,
hair color, and height

6. Examples of Inherited Traits
Attached or unattached Can you roll your
earlobes tongue? Some people
can’t.

7. Hitchhiker thumb
Widow’s peak

8. How genes are passed from generation to generation
Organisms produce gamete cells (sex cells)
that have half the number of chromosomes as
body cells. (haploid – n chromosomes)
The process of one parent’s gamete combining
with another parent’s gamete is called
fertilization.

9. Adults have 2n chromosomes
(diploid cells – 46 each)
If diploid cells fertilized each
other, a cell would end up with
92 chromosomes.
The next generation would
have 184 chromosomes.
Eventually there would be too
many chromosomes in each
cell

10. Instead… Animal cells undergo meiosis cell division to
reduce the number of
chromosomes before
reproduction occurs.
The offspring receives 23
chromosomes from the
maternal (mother) gamete and
23 chromosomes from the
paternal (father) gamete.

11. Meiosis involves two consecutive cell divisions called meiosis I and meiosis II
Meiosis I – Reduction Stage
Just like in mitosis, meiosis cell division begins
with Interphase
– cells undergo normal
functions
- DNA replication.

12. Meiosis I – Prophase I Chromatin coils up, Spindles appear,
Nucleoli disappear,
Synapsis occurs – pairs
of homologous chromosomes form
How is this a little different from
mitosis prophase?

13. Meiosis I
Prophase I
Crossing over produces exchange of genetic information.
Crossing over —chromosomal segments are exchanged between a pair of homologous chromosomes

14. Meiosis I Metaphase I Chromosome centromeres attach to spindle fibers.
Homologous chromosomes
line up at the equator.
How is this different from
mitosis metaphase?

15. Meiosis I Anaphase I Homologous chromosomes separate and move to
opposite poles of the cell.
Centromere not broken
Chromosome number
reduced from 2n to n
How is this different from
mitosis anaphase?

16. Meiosis I Telophase I The spindles break down. Chromosomes uncoil and
form two nuclei
The cell divides,
(cytokinesis).
Two daughter cells
are produced with ½ the
number of chromosomes. (n)

17. Meiosis II continues the cell division
To begin the second set of
meiosis stages, we start
with the daughter cells
from meiosis I.
The DNA will not be
replicated in meiosis II.
If we separate the DNA and divide the cells,
how many cells will be produced?
How many chromosomes in each new cell?

18. Meiosis II – Prophase II
A second set of phases begins as the spindle
apparatus forms and the chromosomes
condense.

19. Meiosis II – Metaphase II
A haploid number of chromosomes
line up at the equator.

20. Meiosis II – Anaphase II
The sister chromatids are pulled apart at the
centromere by spindle fibers and move toward
the opposite poles of the cell.

21. Meiosis II – Telophase II
The chromosomes reach the poles, and the nuclear membrane and nuclei reform.

22. Meiosis II - Cytokinesis
Cytokinesis results in four
haploid cells, each with
n number of chromosomes.

23. Meiosis I and Meiosis II

24. Mitosis Meiosis I and II

25. Males – four sperm made by one cell dividing equally into four.
Mitosis
Meiosis I
Meiosis II

26. Females – one ovum produced
- Unequal division made
during meiosis I and
meiosis II
Only the large cell
survives and is passed on
Extra cytoplasm
provides food for the embryo.

27. The Importance of Meiosis I and II
Meiosis consists of two sets of divisions
Produces four haploid daughter cells that are not identical
Results in genetic variation

28. Meiosis Provides Variation
Depending on how the chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result.
Genetic variation also is produced during crossing over and during fertilization, when gametes randomly combine.

29. Studying a person’s genetic make up
Every person is made
up of trillions of cells,
and each cell carries a
full copy of that person’s
genetic code, in the form
of homologous
chromosomes.

30. How are these karyotypes different?

31. Genetic defects – look closely, how are these karyotypes different?

32. Sexual Reproduction vs. Asexual Reproduction
the organism inherits all
of its chromosomes from
a single parent.
The new individual is
genetically identical to its
parent.
Example – binary fission -- involves an equal division of both the organism cytoplasm and nucleus to form two identical organisms

33. Asexual Reproduction
Vegetative
Propagation
Spores

34. Asexual Reproduction - Regeneration
Body parts that are
missing due to damaged
or predation can be
regrown.

35. Asexual reproduction - Budding
The parent plant grows a
structure (a bud) that
matures, falls off and
grows on its own.

36. Sexual reproduction Beneficial genes multiply faster over time.
2 parents - combination of genetic material not identical
a) egg and sperm (gametes) combine

37. fertilization forms zygote
zygote grows by mitosis
-creates stem cells
unspecialized cell mass of
100 –150 of the first cells to
form.

40. Review of Section 10.1
Each student in class has characteristics passed on to them by their parents.
The instructions for the traits are found on chromosomes in the nucleus.
The DNA on the chromosomes is arranged in segments that control the production of protein
These DNA segments are called genes.
Each chromosome consists of hundreds of genes
Each gene has an important role in determining the characteristics and function of the cell

41. 10.2 Mendelian Genetics How Genetics Began
The passing of traits to the next generation is called inheritance, or heredity.
Mendel performed cross-pollination in pea plants.
Mendel followed seven traits in the pea plants he bred.
Examples: flower color, seed color, height of plant, texture of seed.

42. Self pollenating plant
Cross pollinating plant

43. Mendel’s Experiments – cross-pollination by transferring a male gamete from the flower of one pea plant to the female reproductive organ in a flower of another pea plant.

44. The Inheritance of Traits
The parent generation is
also known as the P
generation.
Cross two pure parents
one yellow & one green
Green trait didn’t
disappear, it was hidden
or masked.

45. Mendel noticed that some pea plants produce yellow seeds and others produce green.
The offspring of this P
cross are called the
first filial (F1) generation. = __?__
All yellow
F1 self-pollinates = F2
¾ yellow and ¼ green
Green trait didn’t
disappear, it was hidden
or masked.

46. Genes in Pairs Mendel concluded there must be two forms of the seed trait in the pea plants
Allele - An alternative form of a single gene passed from generation to generation
The F1 pea plant had one yellow allele and one green allele
Dominant – The allele for yellow seed color is dominant over the green seed color (Y)
Recessive – the allele for green seed color is recessive (y)

47. Law of Dominance
An organism with two of the same alleles for a particular trait is homozygous
Homozygous yellow –seed plants are YY
Homozygous green-seed plants are yy
An organism with two different alleles for a particular trait is heterozygous.= Yy
When alleles are present in the heterozygous state, the dominant trait will be observed.

48. Genotype and Phenotype
You cannot tell an organisms alleles by its outward appearance. Some traits may be masked.
An organism’s allele pairs
are called its genotype
A yellow plant may have a
genotype of YY or Yy, both
allele pairs will produce
yellow seeds.

49. Mendel’s Law of Segregation
Two alleles for each trait separate during meiosis.
During fertilization, two alleles for that trait unite.
Heterozygous organisms are called hybrids

50. Law of Independent Assortment
Random distribution of alleles occurs during gamete formation
Genes on separate chromosomes sort independently during meiosis.
Each allele combination is equally likely to occur.

51. Genotype and Phenotype
The observable characteristic or outward expression of an allele pair is called the phenotype
The phenotype of pea plants
with the genotype of yy will
be green seeds.

52. Genotype compared to Phenotype

53. Predicting Genotypes Punnett Squares and Probability
Predict the possible offspring of a cross between two known genotypes
Each box = 25% chance

54. Monohybrid Cross
A cross that involves hybrids for a single trait is called a monohybrid cross.
Four boxes in the Punnett square.

55. Dihybrid Cross is for two traits
The inheritance of two or more traits in the same plant is a dihybrid cross.
Dihybrids are heterozygous for both traits.

56. Punnett Square—Dihybrid Cross
Four types of alleles (2 traits) from the male gametes and four types of alleles (2 traits) from the female gametes can be produced.
The resulting phenotypic ratio is 9:3:3:1.

57. Cross Test Unknown dominant trait crossed with a known
homozygous recessive,
If offspring show
recessive phenotype,
It is know that the parent
was heterozygous.

58. 10.3 Gene Linkage and Polyploidy
Genetic Recombination is
the new combination of
genes produced by
crossing over and
independent assortment
Sex Chromosomes =
One pair
Female = XX and
male = Xy

59. The X chromosome carries most genes to be passed to offspring.
The X chromosome is the largest, Y being the smallest.
The X chromosome carries genes needed by both males and females
The Y chromosome carries mostly genes for male characteristics.

60. Co-dominance

61. Gene Linkage
The linkage of genes on a chromosome results in an exception to Mendel’s law of independent assortment because linked genes usually do not segregate independently.

62. Incomplete Dominance

63. Chromosome Mapping Chromosome mapping = genes in exact locations on
all chromosomes within
organism
farther apart they are more
likely to cross over,
so a higher percentage of
crossed genes would mean
the genes are farther apart

64. Chromosome map and gene linkage

65. After the crossover, A and B are together with c, and a and b are together with C on one of the two chromatids of the recombined chromosomes

66. Polyploidy Polyploidy is the occurrence of one or more
extra sets of all chromosomes
in an organism
A triploid organism, for
instance, would be designated
3n, which means that it has
three complete sets of
chromosomes.
Strawberries are 8n

67. In humans, polyploidy is lethal, an embryo will not survive.