lecture 10- mendel genetics Flashcards
how many genes are in the human genome
20,000-25,000
are humans identical
identical in 99.9% of gene sequences
where are alleles
on the same loci of homologous chromosomes
what is a locus
place where a gene is on a chromosome
what are the characteristics of a homologous pair
similar size
same number of genes
same genes at the same place
what is a dominant allele
allele that masks the presence of another allele (uppercase letter)
what is a recessive allele
allele that can be masked by the presence of a dominant allele (lowercase letter)
what is BB called
homozygous dominant
what is Bb
heterozygous
what is bb
homozygous recessive
does the allele being dominant have any effect on how common it is
no
what is a genotype
the combination of allele (ex. BB, Bb, bb)
what is a phenotype
the appearance of the characteristic (ex. purple or white)
does knowing the phenotype give us the genotype
no because of heterozygous allele combination
how do recessively inherited disorders occur
when the individual is homozygous recessive only
what is a carrier
someone who carries the recessive gene but displays the dominant phenotype
does the carrier of a disease have that disease
no
how do dominantly inherited disorders occur
when the individual is homozygous dominant or heterozygous
in a dominant disorder are Ff a carrier
no because they display the disease
when crossing heterozygous parents (one dominant one recessive) what is the outcome
all offsprings will display the dominant phenotype but carry the recessive gene
when crossing two carriers with each other what is the outcome
75% will display the dominant phenotype
25% will display the recessive phenotype
what is the law of segregation
the different alleles will always end up in different gametes after meiosis
what is a monohybrid cross
cross between two heterozygous individuals
what is the purpose of a punnett square
determines the probability of an offspring having a particular genotype
do the punnett square give us the for sure result to be expected
no
everything is random so this would only be the expected results from a large scale study
what are the two rules of probability
addition rule
multiplication rule
what is the addition rule
“or”
chances of having a boy or a girl
0.5 + 0.5 = 1
what is the multiplication rule
“and”
chances of having a girl and a girl
(0.5)(0.5) = 0.25
what is a test cross and what is it used for
cross done with a recessive individual
to test whether an organism with a dominant phenotype is heterozygous or homozygous dominant
what is a dihybrid cross
cross with alleles on two different loci (2 genes on different chromosomes)
how do you know how many different combinations of alleles there are
2^n where n is the number of heterozygous alleles
AaBBccDd = 2^2 = 4
how do you know how many combinations of gametes a parent can have (dihybrid cross)
foil the two genes
(Bb)(Ss) = BS Bs, bS, bs
what is the ratio for dihybrid crosses and what is it called
phenotypic ratio
9:3:3:1 (most dominant to least)
