7.1 Inheritance Flashcards
What are the 5 different types of inheritance?
codominant
multiple alleles
sex-linkage
autosomal linkage
epistasis
What is a genotype?
the genetic constitition of an organism = the alleles it has for 1 gene
What is a phenotype?
the expression of genes and its interaction with the environment
What does homozygous mean?
a pair of homologous chromosones carrying the same alleles for a single gene
What does heterozygous mean?
a pair of homologous chromosome carrying two different alleles for a single gene
What is codominant inheritance?
both alleles are equally dominant and expressed in the phenotype
What does multiple alleles mean?
more than 2 alleles for a single gene
What does sex-linkage mean?
a gene whose locus is on the X chromosome
What does autosomal linkage mean?
genes that are located on the same non-sex chromosome
What is epistasis?
when 1 gene modifies or masks the expression of a different gene at a different locus
What is monohybrid inheritance?
cross of characteristics determined by 1 gene
What is dihybrid inheritance?
cross of characteristics determined by 2 genes
What is chi-squared?
statistial comparison between observed and expected results
How can you tell something was by chance due to deviation from the expected (chi-squared)?
deviation from what was expected is small
How can you tell something was by bias due to deviation from the expected (chi-squared)?
deviation from what was expected is large
What is the chi-squared equation?
sum of (O-E)^2 / E
E = expected value
O = observed value
How do you calculate the expected value E?
sum of observed x phenotype ratio / sum of ratios
How do you calculate the degrees of freedom?
number of categories (phenotypes) - 1
What can you conclude if the x2 value is less than the crititcal value @ P = 0.05?
the difference between observed and expected is NOT significant = due to chance
accept H0
What can you conclude if the x2 value is greater than the critical value @ P=0.05?
the difference between observed and expected IS significant = not due to chance
reject H0
what is a dihybrid cross?
a genetic cross where the inheritance of 2 genes is considered at the same time
How did Mendel discover dihybrid inheritance?
found different characteristics in pea plants:
round or wrinkled
green or yellow
purple or white flower
these characteristics are coded by 2 different genes
What does F0 represent?
parental phenotypes = homozygous
What does F1 represent?
first generation after x2 homozygous parents combine = heterozygotes 100%
What must you include in a genetic cross?
parental phenotype and genotype
possible gametes
offspring genotype and phenotype
phenotype ratio
What is the F2 phenotype ratio of monohybrid inheritance?
3:1
What is the F2 phenotype ratio of co-dominant inheritance?
1:2:1
What is the F2 phenotype ratio of dihybrid inheritance?
9:3:3:1
What is the result of crossing over in meiosis?
new combinations of alleles in the gametes
What is the F2 phenotype ratio of autosomal linkage?
3:1
How can you tell if crossing over has occured in autosomal linkage?
other phenotypes that were not expected in the 3:1 ratio are produed = recombinant offspring
What are recombinant offspring?
offspring that have a different combination of characteristics than their parents
Why are homozygous dominant and homozygous recessive offspring most common in autosomal linkage?
their gametes are not as a result of crossing over
What happens when genes become further apart on a chomosome?
the genes are less linked = increase chance of crossing over = increased chance of recombinant offspring
Are females homogametic or heterogametic?
homogametic = XX
Where are the sex-linked genes located on the X chromosome?
in the non-homologous region = Y chromosomes do not have this because they are shorter
Who is more likely to suffere from a sex-linked disorder caused by a recessive allele?
males = they only have 1 X chromosome so it is easier to obtain a recessive allele
What is evidence from a pedigree diagram that a disorder is recessive?
2 non-affected parents produce an affected child
What evidence from a pedigree diagram shows a disorder is NOT sex-linked?
an affected daughter is produced from a non-affected father = the father does not have the recessive allele on his X chromosome
How can you tell from a pedrigree diagram that a disorder IS sex-linked?
only males have the disorder
