inheritance Flashcards
what is a gene
section of DNA that codes for a polypeptide
whats an allele
a version of a gene
whats genotype
the genetic makeup of an organism
whats phenotype
the expression of a characteristic due to environment and genes
whats homozygous
when the alleles of a particular gene are identical e.g both recessive or one h one g
whats heterozygous
when the alleles of a particular gene are different e.g dominant and recessive
whats haploid and diploid
haploid has half the number of chromosomes in a cell than a normal body cell. has 23 chromosomes not in homologous pairs
diploid full number of chromosomes 23 pairs of homologous chromosomes
when are dominant and recessive alleles shown in the phenotype
dominant always shown in phenotype
recessive only shown when in phenotype when there are no dominant alleles. in crosses use same letter
what does multiple alleles mean
term used to describe a gene with more than 2 possible alleles
e.g blood group
whats co dominance
when both alleles are expressed in the phenotype because both alleles are dominant e.g roan hair = red and white together so would be RW
whats sex linked
any gene found on the x or y chromosomes. males xy females xx
what is the common pattern for sex linked conditions
are caused by a mutation of a gene on the x chromosome the mutation usually leads to a non functional protein being made. males only have one x chromosome y is shorter so only need to have1 allele that codes for the non functional protein
why can we use drosophila in experiments
lay lots of eggs
short life cycle
small space needed
not endangered
what are the offspring ratios
monohybrid = 3:1 for the f2 generation Gg Gg
dihybrid = 9:3:3:1
autosomal linkage= 3:1
whats monohybrid inheritance and how to know its a question on it
inheritance of a single gene
one gene
dominant and recessive in 3:1 ratio with heterozygous parents
only this used in hardy Weinberg
evidence of recessive condition in offspring
what’s dihybrid inheritance and how to identify question
how two different genes on different chromosomes are inherited
two genes not on same chromosome
independent characteristics one doesn’t control the expression of the other
9:3:3:1
what’s sex linkage and how to identify question
when any gene is found on x or y chromosomes males have xy females have xx
x and y present
sometimes combned with multiple alleles and co dominance
evidence of recessive sex linked, parents have dominant condition but parents have recessive
whats multiple alleles and co dominance and how to identify q
co dom= both alleles equally dominant leads to expression of both in the phenotype
multiple = where there are more than two alleles of which only two may be present at the loci of an individuals homologous chromosomes
question = phenotype combo of two alleles
denoted with capital letters for each allele
three or more phenotypes present
codominance cant be used for hardy Weinberg multiple alleles can but only two at once
what is epistasis and how to identify question
when the allele of one gene affects or masks the expression of another in the phenotype
two genes
not on same chromosome
one controls the expression of the other
not 9:3:3:1
whats autosomal linkage and how to identify the question
when 2 genes inherited at the same time on same chromosome
the combo of inheritance only altered by crossing over always draw 2x2 grid for AL
A with B and a with b
q = two genes on same chromosome
few offspring with phenotype from heterozygous gametes which only occurs from crossing over
many offspring with phenotype from homozygous gametes
whats an autosome
all 22 chromosomes other than x and y
what does hardy Weinberg predict and the equation
frequency of alleles will stay constant over 1 generation to the next
p2+2pq+q2=1 p+q=1
what are the assumptions for hardy weinberg
random mating no mutations large populations population genetically isolated no migration
what is the evidence from a pedigree chart that proves its a recessive gene that causes a condition
2 parents don’t have condition but child does
parents must be carriers/both parents have condition so all children must do too
evidence from pedigree chart that proves its a dominant gene that causes condition
parents have a condition but child doesn’t
parents have heterozygous alleles condition caused by dominant one child have homozygous recessive
evidence from pedigree chart that proves its sex linked condition
if father has dominant condition daughters will always be dominant
daughters can only have recessive condition if their father is recessive and mother both x recessive
