inheritance Flashcards
(23 cards)
what the genotype
genetic constitution of an organism
what is the phenotype
the expression of this genetic constitution and its interaction with the environment
eg. brown eyes
what is an allele
different versions of a gene
what is homozygous
both alleles at a specific locus on each homologous chromosome are the same
eg. BB or bb
what is heterozygous
both alleles at a specific locus on each homologous chromosome are different
eg. Bb
what is a dominant allele
in heterozygous it is the allele that is expressed in the phenotype
what is a recessive allele
in heterozygous state it’s the allele that isn’t expressed in the phenotype
only expressed if homologous recessive
what is a codominant allele
both alleles for same gene in heterozygous organism contribute to the phenotype
what should genetic inheritance diagrams contain
parent genotype
parent phenotype
parent gamete genotype
punnet square
offspring genotypes labelled with phenotypes
what is monogenetic inheritance
inheritance of characteristics controlled by a single gene
draw a mono hybrid cross from inheritance of wind length in fruit flies
N - normal wings
n - little wings
homozygous dominant parent and homozygous recessive parent
f1 and f2 generations
parent 1 - NN
parent 2- nn
f1- N. N
n Nn Nn
n Nn Nn
all Nn heterozygous
parent 1- N n
parent 2 N n
N. n
N NN. Nn
n. Nn nn
3:1 ratio homo to hetro
normal wings: vestigial wings
what is dihybrid
inheritance is two different characteristics controlled by two different genes
an allele from one pair of chromosomes can entered a gamete with either allele from the other pair of independent segregation so
AaBb can produce gamete AB Ab aB ab
what do crosses involving codominace involve
both alleles in a heterozygous individual contribute to phenotype
eg. coat colour in cattle
red and white allele = roan coat - speckled white and red coat
what do multiple allele crosses involve
individuals only have 2 alleles die a gene but there may be more than 2 alleles
there is usually a dominance hierarchy
what do sex linkage crosses involve
a gene is sex linked ur it’s locus is in a sex chromosome
specific characteristics more likely to be inherited in either female or male offspring
genes are more likely to be X linked
females have tow copies of gene (XX)
- only express recessive if homozygous recessive
males have one copy of gene (XY)
- can’t be heterozygous, express recessive X linked allele is only one copy present
what do autosomal linkage crosses involve
two genes carried on same autosome
genes stay together during independent segregation so assuming no crossing over all linked genes remain together during meiosis
therefore linked genes pass into gametes together
higher proportion of offspring will have parents genotype and phenotype
draw a pair of chromosomes autosomally linked with Tr and tR vs a pair of chromosomes not autosomally linked
T | T t | t
| |
r. | r R |. R
Tr. tR
what is epistasis
interaction of non linked genes where one masks the expression of the other
give an example of epistasis in mice
A - dominant albino
a - recessive black
B - dominant production of melanin
b- recessive no production of melanin leads to white
draw a genetic cross of an agglutination homozygous dominant mice and a white homozygous recessive mouse
AB. Ab. aB. ab
AB
Ab
aB
ab
9 brown agouti: 4 albino :3 black
what is chi squared test
stats test to find whether the difference between expected and observed data is due to chance
when to use a chi squared test
the data is in categories
the data is frequency
how would you carry out a chi squared test
- define null hypothesis
- there is no significant difference between… any difference i’d use to chance - calculate chi squared
- determine degrees of freedom ( categories -1)
- determine critical value at p = 0.05
- interpret results - value has to be equal to or larger than critical value
