4/22 Flashcards
if you have three heterozygotes, how many gametes do you have?
2^n = n=3, 8 types of gametes
what does it mean to be true breeding
it means the organism is homozygous
if a trait disappears in one generation, but comes back in another, what type of allele is it
it is recessive
if a trait is always present, what type of allele is it
it is dominant
if the recessive phenotype is being expressed, what does this tell us about the dominant allele?
it is not present
what is a loss of function allele
a mutated gene that has lost its normal function so the individual requires two copies of the allele to be expressed. This is inherited in a recessive manner
how is green a loss of function allele
the enzyme that codes for the yellow color is not active in the mutated y gene, so having two yy will only give a green color
if you have Yy, why does the loss of funciton allele not dominate?
you still have one functional allele, this allows for the yellow color making enzyme to still be expressed
if you have two parents that do not show a phenotype for an allele, but have offspring that do, what type of transmission is this?
horizontal transition through recessive inheritance
if you have a parent that has a phenotype for a disease and this disease phenotype rarely goes away in offspring, what type of transmission is this
vertical transmission through dominant inheritance
why is inbreeding generally harmful?
if a recessive allele is passed from the same family line, offspring of inbreeding are more likely to be homozygous recessive and have a higher chance of disease
what is homogametic
the sex produces only one type of gamete (X)
what is heterogametic
the sex produces two types of gametes (XY)
in terms of sex chromosomes, how do mammals and avians differ
in mammals, males are heterogametic and have the sex determining chromosome
in avians, the females are heterogametic and have the sex determining chromosome
in avians, what is the genotype of males and females for their sex chromosomes
males are ZZ and females are ZW
what does it mean if a gene is pseudoautosomal?
it means it is also on the Y chromosome and will behave like a normal cross
what is pseudoautosomal inheritance
genes found on both X and Y chromosomes, this allows theme to follow the same inheritance pattern as an autosome
what is a reciprocal cross
crosses between different strains in which the sexes are reversed
what does a reciprocal cross show?
it reveals whether a trait is carried on a sex chromosome or an autosome
what is a male test cross? what is the purpose?
a male test cross is where the male has the recessive gene on the X chromosome only but still shows the phenotype
this tells us about the genotype of the female
why do X-linked genes often cause issues in males
males only get one X chromosome, so whatever gene is on X chromosomes is what will be expressed in the males
what does hemizygous mean?
it means that males have only one copy of the X-chromosome
what is a sex-linked gene?
genes that are found on one of the two types of sex chromosomes
who can pass an X-linked gene to a son?
only the mom
