Do Now!!  True or False? 1. Certain thoughts or experiences of a mother mark or alter the hereditary makeup of an unborn child. 2. Color blindness is more common in males than in females. 3. A person may transmit characteristics to offspring which he/she does not show. 4. Certain inherited traits may be altered by the stars, planets or moon early in development. 5. The total number of male births exceeds female births each year.

Allele: Version of a gene Dominant: shields recessive trait (ex: B=brown eyes) Recessive: masked by dominant (ex: b=blue eyes) Heterozygous: 2 different alleles (ex: Bb) Homozygous: 2 of the same alleles (ex: BB, bb) Genotype: organism’s set of genes (ex: BB, Bb, bb) Phenotype: physical appearance (ex: brown or blue eyes)

Chapter 10: Genetics!

Objectives To distinguish between heredity and inheritance To describe Mendel’s experiments in heredity To compare heterozygous vs. homozygous and dominant vs. recessive.

Do Now!!  Ariel and Prince Eric are curious to see what their babies will look like! Eric is heterozygous for black hair and Ariel has the recessive trait of red hair. Both are recessive for blue eyes. If they have 32 children, how many can we EXPECT to have red hair and blue eyes?

Do Now!!  Mickey Mouse is heterozygous for round ears and homozygous for black eyes. Minnie Mouse is homozygous for floppy ears and heterozygous for black eyes. Determine phenotype ratios.

Genetics: the study of heredity by which traits are passed from parents to offspring

Gregor Mendel The father of genetics! First to develop rules that accurately predict patterns of heredity Discovered how traits were inherited in a population using pea plants

The beginning of genetics… The passing of traits to the next generation – inheritance or heredity Mendel performed cross-pollination and self-fertilization in pea plants Mendel followed various traits in the pea plants he bred

7 Traits Mendel Studied

Pollination: transfer of pollen from anthers to stigma in flowers 1) self pollination occurs within the same flower or same plant 2) cross pollination occurs between different plants

Mendel’s Crosses with Pea Plants X Pure tall plants Pure short plants parental generation P1 Cross Pollination first filial generation All Tall plants F1 Self Pollination second filial generation 787 tall plants, 277 short plants F2 3 to 1 ratio

Generations P Generation Parents Pure bred F1 Generation Hybrid – 2 different types of genes for a trait F2 Generation 3:1 ratio

Mendel’s 3 Laws of Inheritance Law of Dominance- Each trait is controlled by 2 factors: Dominant- what is expressed Recessive- masked in presence of dominant P1 F1 F2

Mendel’s 3 Laws of Inheritance (cont.) 2. Law of Segregation- Each allele separates into different gametes (when does this happen??) Ex. Ww – one W goes in one sperm and the other w goes into another sperm Ww w W

Mendel’s 3 Laws of Inheritance (cont.) 3. Law of Independent Assortment- Gene pairs (homologous) will separate randomly into gametes during meiosis *Chromosomes line up randomly at metaphase plate

Do Now!!  (P. 6) What were the results of Mendel’s experiments for F1 and F2 generations? What are his 3 laws? What is a gene?

Definitions *genes occur in pairs Gene – segment of DNA on a chromosome that codes for a particular protein *genes occur in pairs

Allele – alternative form of a gene Dominant capital letter (shields recessive trait) T = tall t = short G = green pods g = yellow pods Recessive Lowercase letter (usually hidden)

More alleles!

Phenotype – physical characteristics of an organism (Ex: Blue eyes or Brown Eyes)

Genotype -genetic makeup of an organism (genes) -alleles received from parents (internal information Ex: BB, Bb, bb)

Genotype vs. Phenotype TT Tall genotype phenotype

Homozygous – when both alleles of a pair are the same dominant TT homozygous recessive tt

Heterozygous – when both alleles of a pair are not the same (tall) Tt

for black hair… (H=Black, h=blonde) 1. What is Jon Snow’s genotype? If Jon Snow is heterozygous for black hair… (H=Black, h=blonde) 1. What is Jon Snow’s genotype? 2. What is Jon Snow’s phenotype? Beyonce is BB. (B= brown eyes, b=blue eyes) 1. What is her genotype? 2. What is her phenotype? 3. Is she heterozygous or homozygous? Explain.

Genotypic vs. Phenotypic Ratios Phenotype Ratio: Ratio of different physical traits Ex) Brown eyes ¼ or 25% Genotype Ratio: Ratio of the different possible alleles Ex) Tt = ¼ or 25%

Monohybrid Cross R= Can roll your tongue r= Can’t roll your tongue Genotype Ratio: Phenotype Ratio: R r

Lets Try a Monohybrid together! Daffy Duck is heterozygous for black feathers. Daisy Duck is homozygous for yellow feathers. Set up a punnett square and determine probabilities of their potential offspring. (Both genotype and phenotype ratios!) B = Black b = yellow

DO NOW!!  Sleeping Beauty has freckles. Her prince charming is heterozygous for no freckles. What are the chances of her children having freckles? Please show your work.

Test cross – an individual with unknown genotype is crossed with a homozygous recessive individual used to determine the genotype of any individual whose phenotype is dominant

Lets Try a Test Cross Spongebob squarepants doesn’t know whether or not he is Homozygous Dominant or Heterozygous for his yellow color. The recessive trait is a white sponge. Let’s say that we perform a “test cross” on spongebob (spongebob + a white female sponge) and all of the baby sponges are yellow. What would spongebob’s genotype be?

What is a dihybrid Cross? A dihybrid cross allows us to predict possible outcomes of offspring that will have 2 traits simultaneously. Ex: what would you get if you crossed a Brown-haired brown-eyed male with a blonde-haired blue-eyed female? How many of the children would have brown hair and brown eyes? Brown hair and blue eyes? Blonde hair and brown eyes? Blonde hair and blue eyes?

Setting up Dihybrid Crosses 1. Labels!! 2. Determine parent genotypes 3. Determine gametes (alleles to be passed down) The FOIL method 4. Set up punnet square 5. Determine outcome Phenotype Ratio

Dihybrid Crosses Looking at two different traits Ex. Hair color and eye color B=brown eyes b=blue eyes R=Brown hair r=blonde hair Mother is heterozygous for both traits Father is heterozygous for eye color and homozygous dominant for hair color

Example

More Practice Mickey Mouse is heterozygous for Round ears and homozygous for Black eyes. Minnie Mouse is homozygous for Floppy ears and heterozygous for Black eyes. Determine phenotype ratios. (B=black eyes, b=brown eyes, R=round, r= floppy.)

Gene Linkage There are several genes on a chromosome Gene Linkage: When two genes are close to each other on the same chromosome

Gene Linkage (cont.) Linked genes on a chromosome results in an exception to Mendel’s law of independent assortment Linked genes usually do not segregate independently

Drosophila melanogaster (Fruit Flies) First organism with linked genes Linked genes typically travel together during crossing over

Chromosome Map A map of genes on chromosomes Crossing over occurs more frequently between genes that are far apart

Strawberries are octoploid!! Polyploidy Cells that contain more than 2 homologous sets of chromosomes Ex. A triploid organism (3n) - means that it has three complete sets of chromosomes. Strawberries are octoploid!!

Pedigree Shows history of a trait in a family Allows researchers to analyze traits within a family

In a pedigree… You can see how a genetic disorder runs in a family. Carriers are individuals who are heterozygous for an inherited disorder but do not show symptoms. Carriers can pass the allele for the disorder to their offspring

Symbols for Pedigree

Figure out each genotype!

Do Now!!  Fill in the genotypes for the following pedigree (shows recessive trait) B=brown eyes b = blue eyes

Incomplete dominance Red + White = Pink Heterozygous phenotype is intermediate between two homozygous phenotypes: In between two extremes Heterozygous phenotype appears blended. Ex: Four O’clock flowers Red + White = Pink

Codominance Both traits are dominant and expressed (no blending) Ex: Roan Cows white hair (HW) is codominant with red hair (HR) cows with genotype (HRHW) have coats with a mixture of red and white hairs (roan) Red + White = RED AND WHITE

Do Now!!  What is the difference between incomplete and codominance? Cross a roan cow with a red cow.

Multiple alleles – 3 or more alleles that control a trait Example: blood type! Possible alleles: IA, IB, i Which genotypes are heterozygous? Homozygous? GENOTYPES RESULTING PHENOTYPES IAIA IAi Type A IBIB IBi Type B IAIB Type AB ii Type O

Antigens vs. Antibodies Antigen: substance foreign to the body that causes an immune response: Can act as surface markers EX: type A antigens on surface of type A blood cells Antibody: protein that reacts with specific antigen: EX: Type B blood contains anti-A antibodies

Which is the universal donor? Universal acceptor?

Determine Blood Type Determine the possible offspring of the following crosses 1. AB and O 2. Homozygous A and heterozygous B 3. AB and AB

What do you see?

What do you see?

Sex Linked Traits Traits located on the sex chromosomes (X or Y) X linked: gene is located on the X chromosomes Y linked: gene is located on the Y chromosome Ex: color-blindness is X-linked! *If X-linked, can males be carriers?

Sex-Linked Traits A man who is color blind marries a woman that is heterozygous for color blindness. What is the chance of having a color blind boy?

Polygenic Traits Polygenic traits arise from the interaction of multiple pairs of genes.