Chapter 10.2 & 10.3 Genetics

10.2 Vocabulary Genetics Allele Dominant Recessive Homozygous Heterozygous Genotype Phenotype Law of Segregation Hybrid Law of Independent Assortment

Section 2 Mendelian Genetics Standards: 4.2, 4.6, 4.7 Objectives: Explain the significance of Mendel’s experiments to the study of genetics. Summarize the law of segregation and law of independent assortment. Predict the possible offspring from a cross using a Punnett Square.

Review Sexual Reproduction: DNA for offspring comes from different individuals – Parents: father & mother Fertilization: 1 gamete from each parent fuse to form offspring – Each gamete donates ½ amount of DNA needed Male gamete = sperm/pollen Female gamete = egg

Review DNA is divided into units called genes Genes code for proteins Proteins control how you look The passing of this genetic information from parents to offspring is called heredity

Gregor Mendel “Father of Genetics” – Genetics – study of heredity 1866  published finding of Inheritance (traits passed from generation to the next). Studied pea plants

Mendel’s Experiments Mendel studied 7 different pea characteristics. – Characteristic = GENE Each characteristic had 2 different variations. – Variation = ALLELE (alternative form of a single gene)

Mendel’s Experiments Mendel controlled which plants bred with each other through a process called cross-pollination.

Mendel’s Experiments Mendel bred plants with different traits to see what kind of traits the offspring would have. X Purple Flowers White Flowers X Purple Flowers

Mendel’s Experiments Mendel started each experiment with purebred plants expressing a specific trait. – Purebred – organism that expresses and passes on unchanging traits from generation to generation. X X Purebreds P Generation

Mendel’s Findings After cross-pollination, Mendel noticed… 1.Some forms of a trait always appeared 2.Some forms of a trait always disappeared 3.Traits that disappeared would reappear in the next generation IF he let the plants self pollinate. X X X Self-pollinate Cross-pollinate Purebred 1 st Generation (F1) 2 nd Generation (F2)

Mendel’s Findings Purebred X X X Self-pollinate Cross-pollinate Purebred 1 st Generation (F1) 2 nd Generation (F2)

Mendel’s Findings

Mendel’s Law of Dominance Forms of a trait that “disappear” are really hidden by the other form of the trait. – Hidden (or masked) traits  Recessive  lowercase letter – Traits that appear & do the hiding  Dominant  capital letter

Genotype/Phenotype Genotype – combination of allele pair – Genetic makeup – Represented by letters – Example: F = long fur; f = short fur Phenotype – observable characteristic of allele pair – Physical features – Example: long fur or short fur

Mendel’s Law of Segregation All organisms have two copies per gene. Parents carry two copies of each trait and that they separate from each other during meiosis II. Each gamete receives 1 of the 2 alleles (= chance) that parent carries. During fertilization (sperm & egg unite)  two alleles unite. Each parent passes one copy of its traits  offspring look similar but not exact.

Mendel’s Law of Segregation

Homozygous/Heterozygous Homozygous  SAME alleles for a specific trait – Homozygous Dominant  only pass on a dominant form of a trait; 2 capital letters (AA) – Homozygous Recessive  only pass on a recessive form of a trait; 2 lowercase letters (aa) Heterozygous  DIFFERENT alleles for a specific trait – Heterozygous  able to pass on the dominant & recessive forms; 1 capital & 1 lowercase (Aa) – Also called Hybrids Pp = Heterozygous

Homozygous/Heterozygous X X X AA _____ aa _____ aa _____

Mendel’s Law of Independent Assortment Different forms for each trait have the same chance of being inherited  no 1 trait prevents the inheritance of another (unless genes are linked). Genes on separate chromosomes separate independently during meiosis. – Example: flower color can not affect the inheritance of seed color. This is why there are so many possible combinations of traits that can occur!

Punnett Square Tool used to predict possible allele combinations in offspring. – Must know parent genotypes Monohybrid Cross Inheritance of a single trait. – 1 gene, 2 alleles – 4 boxes Dihybrid Cross Inheritance of two traits. – 2 genes, 4 alleles – 16 boxes

How to Use a Punnett Square Step 1: List dominant and recessive phenotypes  assign letters. – Always use the same letter for the same gene/characteristic! – Dominant  UPPERCASERecessive  lowercase

How to Use a Punnett Square Step 2: What are the parent genotypes? – Think of the possible parent genotypes based on offspring. – Homozygous (same)  if parent only produces one type of a trait – Heterozygous (different)  if parent produces both types of a trait

How to Use a Punnett Square Step 3: Determine what information you are trying to find out. – Offspring genotypes – Offspring phenotypes – Ratios for both Step 4: Draw Punnett Square – Monohybrid (4 boxes) or Dihybrid (16 boxes)

How to Use a Punnett Square Step 5: Write alleles or both parents on Punnett square (one on top and one down the side)

How to Use a Punnett Square Step 6: Cross Parents Step 7: Analyze Results Genotypes Phenotypes y y y YY yy yy yy Y

1) Monohybrid Practice In rabbits, black fur is dominant to white fur. If you cross a homozygous male black dog to a heterozygous female black dog, what are the possible genotypes and phenotypes of the offspring? GenotypesPhenotypes

2) Monohybrid Practice In cabbage butterflies, white wings are dominant to yellow wings. A heterozygous butterfly is crossed with a homozygous yellow butterfly. GenotypesPhenotypes

3) Monohybrid Practice In dogs, there is a hereditary type of deafness caused by a recessive gene. Two dogs who carry the gene for deafness but have normal hearing are mated. GenotypesPhenotypes

4) Monohybrid Practice In guinea pigs, short hair is dominant over long hair. A homozygous short haired one is crossed with a homozygous long haired guinea pig. GenotypesPhenotypes

5) Dihybrid Practice Black hair is dominant over blonde hair and brown eyes are dominant over blue eyes. Father is heterozygous for black hair and brown eyes and mother has blonde hair and blue eyes.

6) Dihybrid Practice Black hair is dominant over blonde hair and brown eyes are dominant over blue eyes. Both parents are heterozygous for both traits.

10.3 Vocabulary Genetic Recombination Polyploidy

Section 3 Gene Linkage and Polyploidy Standards: 4.2, Objectives: Summarize how the process of meiosis produces genetic recombination. Explain how gene linkage can be used to create chromosome maps. Analyze why polyploidy is important to the field of agriculture.

Genetic Recombination Genetic Recombination – new combination of genes produced by crossing over and independent assortment. – Increases genetic diversity! – 2 n (n = # of paired chromosomes)  each gamete Example: Pea plants have 7 pairs of chromosomes Example: Human have ______ pairs of chromosomes.

Gene Linkage Genes close on the same chromosome are “linked” and travel together during meiosis  inherited together. – Linked genes do not segregate independently exception to independent assortment

Polyploidy Most organisms have diploid cells. Polyploidy – one or more extra sets of all chromosomes in an organism. – Triploid  3 complete sets of chromosomes  3n – Rarely occurs in animals; humans = lethal – Occurs in flowering plants  increased size Strawberries are 8n.

Chapter 11 Complex Inheritance & Human Heredity

11.1 Vocabulary Carrier Pedigree

Section 1 Basic Patterns of Human Inheritance Standards: 4.7 Objectives: Analyze genetic patterns to determine dominant or recessive inheritance patterns. Summarize examples of dominant and recessive disorders. Construct human pedigrees from genetic information.

Recessive Genetic Disorders A recessive allele codes for a faulty protein. Carrier – an individual that is heterozygous for a recessive disorder. – 50% chance of passing a recessive allele to their child. – AA  no disorder – Aa  no disorder but a carrier for it – aa  disorder

What is the % a child could have a recessive genetic disorder?

Recessive Genetic Disorders

Dominant Genetic Disorders A dominant allele codes for a faulty protein. – Only one parent needs to have one copy of the defective allele in their gametes to pass the disorder to their children. – AA and Aa  disorder – aa  no disorder

Pedigree Pedigree – diagram that traces the inheritance of a particular trait, disease, or disorder through several generations. – Used to infer genotypes by observing phenotypes. – Dominant traits easier to recognize. – Accurate records of family history  predict effects in future offspring.

MalesSquares Femalescircles Expresses Traitfilled No Traitunfilled Carrier for Traitpartially filled Roman Numeralsgenerations (P1, F1, F2) I, II, III Numbersbirth order of offspring 1, 2, 3

Pedigree

Albinism – Recessive Trait 1.Phenotypes? – AA = ___________________________ – Aa = ___________________________ – aa = ___________________________ 2.Draw a punnett square & record the genotypes:

Albinism – Recessive Trait 3.Children? 4.Gender of children? 5.Generations? 6.Carriers? 7.Assume the 3 rd child mated with an albino male, how likely is it that their child will be albino?

Albinism – Recessive Trait 1.Record genotypes. 2.Children from original couple? 3.Grandchildren? 4.Grandchild gender? 5.Carriers?

Dwarfism 1.Affected individuals? 2.Dominant or Recessive Trait? 3.Genotype of A, B, C, D? 4.Generations?

Phenylketonuria (PKU) 1.Affected individuals? 2.Dominant or Recessive Trait? 3.Genotype of A, B, C, D?

11.2 Vocabulary Incomplete Dominance Codominance Multiple Alleles Sex Chromosome Autosome Sex-Linked Trait Polygenic Trait

Section 2 Complex Patterns of Inheritance Standards: 4.6 Objectives: Distinguish between various complex inheritance patterns. Analyze sex-linked and sex-limited inheritance patterns. Explain how the environment can influence the phenotype of an organism.

Incomplete Dominance Incomplete Dominance – heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes. – Neither allele is completely dominant. – Blend of both the dominant & recessive alleles.

Codominace Codominance – both alleles are expressed in the heterozygous condition at the same time. – Both alleles act dominantly – Both expressed in phenotype – Example: Sickle-Cell Disease

Multiple Alleles: Blood Typing Multiple Alleles – having more than two alleles for a specific trait. Red blood cells (RBC) are covered in proteins called antigens that help cells identify each other. – 3 Types of alleles exist for blood (A, B, O) – 4 Blood Types: Type A Type B Type AB Type O

Multiple Alleles: Blood Typing Possible Allele Combinations A i A (homozygous) i A i (heterozygous) B i B (homozygous) i B i (heterozygous) AB i A i B (heterozygous) O i (homozygous) Blood Types

Blood Typing Practice What are the possible offspring blood types if mom is homozygous Type A and dad is homozygous Type B?

Blood Typing Practice What are the possible offspring blood types if mom is heterozygous Type A and Dad is heterozygous Type B?

Blood Typing Practice What are the possible offspring blood types if mom is Type AB and dad is Type O?

Blood Typing & Compatibility Donated blood MUST be compatible with the recipient’s blood type or receiver may die. Type O = Universal Donor Type AB = Universal Receiver

Sex Determination Sex Chromosomes – determines an individual’s gender; two types: X and Y. Autosomes – any chromosome that is NOT a sex chromosome. Normal Humans have 46 chromosomes: – 44 autosomes and 2 sex chromosomes – Female has XX and Male has XY

Sex Determination Problem What is the probability of a man and woman having a baby girl?

Sex-Linked Traits Sex-Linked Traits – characteristic controlled by genes on the X or Y chromosome. X Linked  traits found on the X chromosome – expressed in males & females Y-Linked  traits found on the Y chromosome – expressed only in males

Dominant X-Linked Traits Trait is expressed in females and males, if they have 1 copy of the dominant allele. – Male  X A Y – Female  X A X A or X A X a Trait is NOT expressed if male has 1 copy of the recessive allele and female has 2 copies of the recessive allele. – Male  X a Y – Female  X a X a

Recessive X-Linked Traits Trait is expressed only in females that have 2 copies of the recessive allele. – Female  X a X a Trait is expressed only if males have 1 copy of the recessive allele – Male  X a Y

Sex-Linked Trait Practice Circle those affected by a dominant X-linked trait. X B X b X c YX d X d X R X R X N Y Circle those affected by a recessive X-linked trait. X a X a X L YX T X t X Z X Z X p Y

Sex-Linked Trait Practice The trait for red-green colorblindness is a recessive X-linked trait. The mother is a carrier for colorblindness and the father is not color blind, what is the probability that they will have a child that will be color blind?

Sex-Linked Trait Practice In fruit flies red eye color is dominant to white eyes. In a cross between two flies 50% of the male & female offspring had red eyes and the other 50% had white eyes. What are the genotypes & phenotypes of the parents?

Sex-Linked Trait Practice Hemophilia is a recessive disorder of the blood. Two normal parents have a son that has hemophilia, what is the probability that they will have a daughter that has hemophilia?

Sex-Linked Trait Practice Hairy ears is inherited as a Y-linked trait. A man with hairy ears marries a woman with normal ears. What is the probability that they will have a female child with hairy ears? Male child with hairy ears?

Sex-Linked Trait Practice This disease is inherited as a sex-linked dominant disease? An affected male marries a homozygous recessive female. What is the probability that they will have an affected daughter? Affected son?

Polygenic Traits Polygenic Traits – characteristic that result from the interaction of multiple gene pairs; produce a high level of variation. – Examples: skin color, height, eye color, fingerprint – Shows bell shaped curve when dominant alleles are graphed.

Environmental Influences Sometimes, changes in the environment can affect how a gene functions. Environment has an affect on phenotype. – Sunlight & Water – Temperature – Diet & Nutrition – Ecological Factors (weather, soil nutrients, toxins)

Heredity/Environmental Influences How do you determine if the expression of a certain trait is a result of heredity or environmental influences? – Scientists study identical twins  same genetics  inherited traits will be expressed in both individuals. Traits that appear frequently  Heredity Traits expressed differently  Environment

11.3 Vocabulary Karyotype Telomere Nondisjunction

Section 3 Chromosomes and Human Heredity Standards: 4.5, Objectives: Distinguish normal karyotypes from those with abnormal numbers of chromosomes. Define and describe the role of telomeres. Relate the effect of nondisjunction to Down Syndrome and other abnormal chromosome numbers. Assess the benefits and risks of diagnostic fetal testing.

Karyotype Karyotype – picture of homologous chromosomes arranged in decreasing size. – Shows number and type of chromosomes present. Individual 1 Individual 2

Karyotype

Telomeres Telomeres – protective cap made of DNA that is found on the ends of chromosomes. – Dysfunctional telomeres have been associated with aging and cancer. Telomere

Nondisjunction Nondisjunction – cell division in which sister chromatids do not separate correctly  cells having abnormal number of chromosomes  chromosomal disorders. – Normal = 46 – Any number other than 46 = Abnormal Only 1 chromosome copy = monosomy 3 chromosomes of one type = trisomy – Nondisjunction = serious disorders  often fatal.

Nondisjunction Can occur with autosomes and sex chromosomes. – Turner’s Syndrome – female is missing X chromosome – Triple X Syndrome – female with 3 X chromosomes – Klinefelter’s Syndrome – male with XXY – Death – male just receives Y chromosome & no X

Nondisjunction

Down Syndrome Also called Trisomy 21 Nondisjunction of chromosome #21 Symptoms: distinct facial features, mental retardation, short stature, heart defects. Affects 1/800 Frequency increases with mother’s age.

Fetal Testing Tests that provide genetic information on developing fetus. Benefits  diagnosing chromosomal abnormalities early Risks  miscarriage & infection

Additional STUFF Genetic Engineering – process of replacing specific genes in an organism so that they express a desired trait. – Gene Map – shows the relative location of each known gene on a chromosome. Genome – all the genetic material in an organism  “Human Genome Project” Cloning – copying a gene or organism. – Naturally or genetic engineering – Benefits  Organ transplants or saving endangered species – Risks  genetic disorders or health problems Gene Therapy – scientists insert normal gene into absent or abnormal gene