exam 3 ppt 1 Flashcards
definition of genetic variation
genetic differences that exist among individuals in a population at a particular point in time
definition of genotype
the genetic makeup of a cell or organism- what combination of alleles is present
exps of genotypes
PP, Pp, pp
definition of phenotype
an individual’s observable characteristics (i.e. height, eye color, weight, color blindness, etc)
exp of phenotype
purple vs. white flowers
definition of alleles
the different forms of any gene
what do alleles correspond to?
changes in the DNA sequence
do we all have the same genes?
yes, we all have the same genes, but just different alleles of them
how many copies of every gene do we have? why?
we have 2 copies of every gene, because we’re diploid
what does it mean if an individual is homozygous?
it means that both alleles are the same (either homozygous dominant or recessive)
what does it mean if an individual is heterozygous?
it means that their two alleles for a gene are different
exp of a homozygous genotype
BB or bb
exp of a heterozygous genotype
Bb
who is Gregor Mendel?
he is the father of modern genetics
what did Mendel study?
he studied the results of hybridization, where two different varieties of pea plants were interbred
what plants did Mendel work with?
pea plants
what strains did the pea plants have that Mendel worked with?
these strains were true breeding (pure line)
what does it mean if a strain is true breeding (pure line)?
it means that every offspring is identical to the parent
what were the two different types of fertilization involved in pea plant hybridization?
self-fertilization and cross-fertilization
explain the self-fertilization in pea plant hybridization
the male organs of the plant produce pollen grains which produce sperm cells, and the female organ receives the pollen
explain the cross-fertilization in pea plant hybridization
plant with greed seeds crossed with plant with yellow seeds; collect pollen from one individual and transfer it to the female organ of a flower on another plant whose male organs have been removed
definition of a trait
variation in physical appearance of a heritable characteristic = phenotype
what is the trait called that appears in the F1?
the dominant trakt
what is the trait called that does NOT appear in the F1?
recessive
what were the results of Mendel’s single-trait (monohybrid) cross with the round vs. wrinkled seed trait?
in the parental generation, male parents produce round seeds while female parents produce wrinkled seeds; the F1 generation all produce round seeds (all heterozygote)->. plant, grow, and allow to self-fertilize; the F2 generation produce a 3:1 phenotypic ratio with 75% round seeds, 25% wrinkled seeds
when does segregation occur in Mendel’s monohybrid cross of round vs. wrinkled seeds?
segregation occurs in the F2 generation at a ratio of 3:1
list of all of Mendel’s monohybrid crosses
seed shape, seed color, pod shape, pod color, flower color, flower and pod position, stem length
what are yellow and green seeds the result of?
they’re the result of two different alleles of the same gene
what does true breeding mean for the cross for seed color?
it means that these lines are homozygous
what are the genotypes used in the seed color Mendel experiment?
yellow= YY, green= yy (same trait, same letter)
is the dominant allele capitalized or lower case when written out?
the dominant allele is a capital letter, the recessive allele is a lowercase letter
what results in the F1 generation of the monohybrid cross for seed color?
the trait that appears, yellow seeds, is dominant and green seeds are recessive; due to crossing two true-breeders in the parental generation, all children in F1 generation are heterozygote (Yy) but still exhibit yellow seed color
what does the principle of segregation talk about?
it discusses the separation of alleles into different gametes
what happens to the alleles in a heterozygote individual?
in a heterozygote, both alleles are present and expressed, but observe dominant phenotype
explanation of Mendel’s parental cross between two homozygotes
homozygous father (RR) and homozygous mother (rr) -> make gametes that go into punnett square- male is R, female is r; the F1 generation results in all Rr offspring (heterozygotes) and all round seeds (dominant phenotype)
explanation of Mendel’s parental cross between two heterozygotes
this explains the F2 generation; heterozygous mother from F1 (Rr) with heterozygous father from F1 (Rr), both have gametes of R and r; offspring in F2 generation have genotypes of 25% RR, 50% Rr, and 25% rr and have phenotypes of 75% round (dominant), 25% wrinkled
what are the phenotypic and genotypic ratios always seen in F2 generations?
1:2:1 genotypic ratio, 3:1 phenotypic ratio
how does segregation occur in the breeding of heterozygous plants?
Aa plants produce gametes A and a, 50% each = segregation
when does the segregation of alleles occur?
this occurs during meiosis
what does segregation reflect (a part of meiosis)?
segregation reflects the separation of homologous chromosomes during anaphase I of meiosis
when did Mendel discover the principle of segregation?
he discovered this in his monohybrid cross with true breeding parents
what can you use punnett squares to explain?
you can use them to explain how gametes form (equally possible to produce all gamete combinations)
what characteristic are the principles of transmission genetics?
these principles are statistical
what can the principles of transmission genetics be stated as?
they can be stated as probabilities
what must the probability of any genotype be between?
it must be between 0 and 1 (add up to 100%)
what is the probability of getting the genotype aa as a result in a cross between AA x Aa?
0
what is the probability of getting the genotype aa in a cross between Aa x Aa?
1/4 (25%)
is each genetic event unique?
yes
what are the expected progeny (resulting genotypes and phenotypes) from a cross of an AA plant with an Aa plant?
1:1 genotypic ratio (1/2 AA, 1/2 Aa); 1:0 phenotypic ratio (all have dominant phenotype)
what are the gametes that each parent produces in a cross between AA x Aa?
1/2 AA, 1/2 Aa
how does a genotype become a phenotype?
through DNA -> RNA -> protein
