Honors Bio Test on Unit 6 Heredity🪻

Genetic

biological traits that are inherited from a parent

Gene

section of DNA that codes for a specific protein

Trait

a characteristic that is the result of a particular protein made during gene expression

Genotype

The actual alleles an individual inherits from their parents

Phenotype

a physical trait that is expressed as a result of genotype (what it looks like)

Alleles

different versions of the same gene due to mutations

Law of Segregation

Chromosome pairs separate during meiosis 1 so that each gamete receives one allele for a given trait

What determines the physical expression of genes?

Genotype (determines phenotype)

Law of Independent Assortment

homologous chromosome pairs line up randomly in metaphase, so each daughter cell is different with any possible combo of chromosomes

Example of independent assortment

not always paternal chromosomes with other paternals or maternal w/ maternal)

Gene linkage/linked genes

genes that are likely inherited together due to their physical proximity on the same chromosome

What decreases chance of gene linkage?

the farther apart two genes are, the less likely they'll be inherited together due to crossing over

Dominant gene

an allele or gene that when present masks the effect of the recessive gene expressed through phenotypes (capital letter)

Recessive gene

Gene that is hidden when the dominant gene is present; must be homozygous to show (recessive genes only effect the organism if passed down from both parents)

Dominant vs recessive gene

can have three genotypes with only 2 phenotypes

Law of Dominance

Some versions of genes are dominant over others (possible to have 3 genotypes and 2 phenotypes)

What causes dominance?

-if a recessive gene codes for a faulty protein

-dominant allele produces a new or overreactive version of a protein

-Some traits require two working copies

Homozygous

inheritance of 2 alleles that are the same (HH, pp)

Heterozygous

genotype resulting in 2 different alleles

Rule of Probability

if 2 events are independent of each other, the likelihood of both events occurring together is the multiplication of each event

When does the rule of probability apply?

Only if the genes are on different chromosomes

What do the letters on the outside of a Punnett square represent?

the genotype of the parents

What do the letters on the inside of a Punnett square represent?

the possible genotype combinations in the offspring

How are Punnett squares useful tools?

helps us determine certain traits/diseases that could be inherited based on all the possible variations of genotypes and their probabilities

What are the 3 Mendel Laws?

law of dominance

law of segregation

law of independent assortment

What are the exceptions to Mendel laws and complete dominance?

-complex inheritance

-some alleles are not dominant or recessive & many traits are controlled by multiple alleles/genes

Homologous pairs have the same genes but...

are not identical and alleles can be different

Polygenic Inheritance

-when several genes influence a trait (height, skin color, eye color, and weight)

-hint: ranges in phenotypes

Codominance

when the heterozygous genotype results in a phenotype where both alleles are fully and separately expressed

Autosomes

chromosomes 1-44 in a human

Sex-linked

Genes that travel on the X chromosome

Karyotype

A diagram that shows homologous chromosome pairs

Protein

the macromolecule that runs your body and expresses traits

Multiple Alleles

having more than 2 alleles for one gene (not just dominant/recessive)

Chromosome

condensed genetic material

Epistasis

when one gene overshadows another

DNA

macromolecule that has the instructions for making you who you are

Incomplete dominance

when the heterozygous genotype results in a phenotype where the two alleles are blended together (creates 3 possible phenotypes)

Sex chromosomes are:

chromosomes that determine your sex

Can males be carriers?

It's impossible for males to be carriers because they only have 1 X they give to a daughter or 1 Y passed to a son. If they have an X-linked trait, it will be expressed because there's not another X chromosome to mask it.

Carrier

a person who has the gene for a trait or disease, but it's not expressed phenotypically

complete vs incomplete vs codominance

-when dominant present homo & hetero look the same, but different from homo recessive (AA= red & aa= white)

-AA= red, Aa= pink, aa= white

-AA= red, Aa= some red & white, aa= white

How do you know if the genes are linked?

usually if you don't see expected inheritance ratios according to Punnett square

In a dihybrid cross, what is the phenotypic ratio between 2 heterozygous parents?

9:3:3:1

Ex. problem: Labs with black fur almost always have black noses. What kind of inheritance pattern is this? Explain how it's possible.

-Linked genes

-Possible if gene for fur color and nose color are physically close on the same chromosome

#2 Ex. problem: Calico cats have fur that is both black & orange, but calicos are always female. What 2 inheritance patterns does this represent?

-codominance because black and orange both show up separately & equally

-sex linked because only females carry the gene (XF Xf)

#3 Ex. problem: An organism has 3 different versions of gene Tyx- version a, b, and c. What inheritance pattern is this? All possible genotypes?

-multiple alleles

-genotypes: aa, bb, cc, ab, ac, bc