Intro to Mendel Genetics

Discrete particles

particles are separate units of matter that exists as an individual entity with spaces between it and other units

In Diploid individuals…

each offspring gets a particle from each parent

Segregation of alleles

Allele pairs separate during the formation of sex cells (gametes), so that each gamete receives only one allele for each gene.

Independent assortment

Independent assortment means that the alleles for one trait are sorted into reproductive cells independently of the alleles for any other trait.

Loci

refers to the specific physical location or "address" of a gene or DNA sequence on a chromosome.

homozygotes

an organism that has two identical alleles (versions of a gene) for a specific trait at a particular genetic locus (like aa or AA)

 

First filial generation

the initial group of offspring resulting from a cross or mating between two distinct parental (P generation organisms)

Second filial generation

the parents kids have kids

first backcross

A cross between a first filial generation hybrid back to one of its two original parents.

Second backcross

a cross between a first filial generation hybrid back to the other original parents.

monohybrid crosses

crosses following a single (mono) trait

what was mendel’s p generation?

two homozygous varieties of peas ( round vs wrinkled peas)

What was mendel’s F1 generation?

All the F1 seeds were round.

What was Mendel’s F2 generation?

He allowed the round peas from F1 to self fertilize. He got ¾ round peas and ¼ wrinkled peas.

What did mendel’s F2 generation tell him?

The traits of the parent plants do not blend. although F1 plants display the phenotype of one parent, both traits are passed to f2 progeny in a 3:1 ration.

What did Mendel Conclude?

• genetic information exists as discrete units occuring in pairs.

• these units are stably transmitted across generations

• the big R form (or allele) at the location (gene) for seed shape codes for wrinkled seed

• the little r alleles codes for wrinkled seed

• the big R alleles displays dominance over the little r in that a heterzygote bigRlittler has the same phenotype (round) as the bigRbigR homozygote

Gene

a genetic factor (region of DNA) that helps determine a characteristic

Allele

one of two or more alternate forms of a gene

locus

specific place on a chromosome occupied by an allele

genotype

set of alleles possessed by an individual organism

heterozygote

an individual organism possessing two different alleles at a locus.

homozygote

an individual organism possessing two of the same alleles at a locus

phenotype or trait

the appearance or manifestation of a character

character or characteristic

an attribute or feature

completely dominant to y, recessive to Y

If the Yy genotype has the same phenotype as the YY genotype

testcross

allows us to determine the genotype by crossing the unknown genotype to a homozygous recessive

Incomplete dominance

the heterozygote can be distinguished from both homozygotes (1 purple: 2 violet: 1 white)

Dihybrid

A breeding experiment that tracks the inheritance of two different traits at the same time

What dihybrid cross experiment did Mendel run?

Mendel ased: do alleles encoding different traits separate independently?

What did mendel’s dihybrid cross experiment result in?

the allele encoding color separated independently of the allele encoding seed shape; producing a phenotypic ration of 9:3:3:1 in the F2 progeny.

Independent assortment

if alleles from different genes are indeed transmitted independently, we can use the AND rule. this occurs when the genes are on different chromosomes

linkage

occurs when the genes are on the same chromosome

goodness-of-fit tests

examine whether observed departures are significantly different from some set of expected values (chi-square test)

chi-square tests for goodness of fit

A statistical tool used to check if sample data match a hypothesized distribution for a single categorical variable. It compares the actual counts you see in your data (Observed, O) with the counts you expect to see (Expected, E) if your null hypothesis is true. Formula = (Oi - Ei)²/Ei over all K classes (basically your total number of things you are testing