Inheritance

define allele

one of two or more alternative versions of a gene

difference between dominant and recessive traits

dominant traits are traits that are visible while recessive traits only have a 25% chance of being seen.

genotype vs phenotype and their relationship

genotypes (genetic composition) code for phenotypes (physical)

mendels law of segregation

explained by the pairing and segregation of homologous chromosome during meiosis

mendels law of independent assortment

alleles of different genes sort independently of each other during the process that gives rise to gametes

concept of probability

chance that an event will have a particular outcome

apply product rule to problems involving genetic crosses

multiplying the probabilities of independent events to find the overall likelihood

relate chromosomes behavior during meiosis to mendel’s laws of independent assortment

random alignment and separation of homologous chromosome pairs during meiosis I, which causes alleles for different genes to be inherited independently.

describe x-linked inheritance patterns and sex chromosomes

genes on the X chromosome show unique patterns due to differences in the number and type of sex chromosomes

why are x linked recessive traits more likely to occur in men

because they only have one x chromosome

dominant and recessive traits in relation to protein function

Dominant traits usually result from alleles that produce a functional or overactive protein, while recessive traits typically arise from alleles that produce a nonfunctional or missing protein

pleiotropy inheritance

occurs when a single gene influences multiple, seemingly unrelated traits, causing one inherited allele to have effects in several parts of the organism.

incomplete dominance inheritance 

neither allele is fully dominant, resulting in a intermediate blend of the two homozygous traits

codominance inheritance 

both alleles in a heterozygote are fully and simultaneously expressed, producing a phenotype that shows both traits without blending.

polygenic inheritance

multiple genes, each with small additive effects, collectively influence a single trait, resulting in continuous variation

how does environment play a role in expression of traits

interacting with genes—factors like temperature, nutrition, stress, or sunlight can enhance, limit, or alter how genetic potentials are expressed.

why do polygenic traits show a continuum of phenotype variation

they are controlled by many genes, each contributing a small effect, so the combined influence produces a wide range of possible outcomes

inheritance

acquisition of traits by their transmission from parents to offspring

gregor mendel

mid 1800s, experimented with pea plants

advantages of the pea plant

genetic variation, self-fertilization, hybridization

true breeding lines

exhibits the same trait over several generations of self fertilization

trait

identifiable characteristic of an organism

character 

general features of an organism 

P generation

true breeding parents

F1 generation

offspring of P cross, can be monohybrids (if parents differ in one trait)

F2 generation

F1 self - fertilizes, recessive trait appears

single factor cross (plant height)

Mendel crossed true breeding tall and dwaft plants (all f1 were tall), allowed f1 to self fertilize, dwarfism appeared in F2 generation (1/4 were dwarf)

genotype

genetic composition of an animal

phenotype

physical/behavioral characteristics

heterozygous

Tt - 2 different alleles, will show dominant trait

homozygous 

TT - identical dominant alleles, tt - identical recessive alleles

law of segregation

alleles of the same gene separate during gamete formation

segregation of alleles

two copies of a gene carried by an F1 plant segregate from each other - each sperm or egg only carries one allele

two factor cross

follows inheritance of two traits, can determine linkage

two factor cross outcome

in f1, offspring are hybrids with respect to both traits, F2 data is consistent with independent assortment 

law of independent assortment

alleles of different genes sort independently of each other during the process that gives rise to the gametes

locus

physical location of a trait

chromosome theory of inheritance

chromosomes are replicated and passed from parent to offspring, genes are found in chromosomes

chromosomes and independent assortment 

explained by chromosome behavior during meiosis, leads to independent assortment of genes found on different chromosomes.

punnett squares

dominant to recessive ratio is 3:1 (TT, Tt, Tt, tt)

probability

chance that an event will have a particular outcome

product rule

probability that two or more independent events will occur is equal to the product of their individual probabilities.

what is the probability of a single child have aa if both parents are Aa?

¼

what is the probability of a three children having aa if both parents are Aa?

1/64th or ¼ x ¼ x ¼