Topic 7A- Genetics Flashcards
Define genotype
The genetic makeup of an organism
Define phenotype
The observable characteristics of an organism, from the genotype and its interactions with the environment.
What are the three types of alleles
Dominant, Recessive and codominant
Define allele
Alternative form of a particular gene, there may be more than one type of allele of a single gene
What are the two types of allele combinations at a specific locus in a diploid organism?
Homozygous and heterozygous
Homozygous refers to having two identical alleles, while heterozygous refers to having two different alleles.
What are the six things you must show in a genetic diagram?
- Parental phenotype
- Parental genotype
- Possible gametes
- Offspring genotype
- Offspring phenotype
- Proportion of each phenotype
What is monohybrid inheritance?
when a phenotype or trait is controlled by a single gene
What is dihybrid inheritance?
Dihybrid inheritance is when two characteristics are studied and is determined by two
different genes that are present on two different chromosomes at the same time
What ratio is expected for a dihybrid inheritance genetic cross?
9:3:3:1
What is codominance?
Where both alleles are expressed equally and contribute to the phenotype
How are genotypes displayed in codominance?
C^x
For example
Give an example of codominance
Blood groups
A and B codominant to form blood group AB
Group O is recessive
What is sex linkage?
When the expression of an allele is dependent on the sex of the individual as the gene is located on a sex chromosome
What chromosomes do men and women have?
Men- XY
Women- XX
Which chromosome is bigger- X or Y?
X
How many of a sex linked gene do women carry compared to men?
Females carry 2 compared to men who only carry 1
Why do recessive alleles on the X chromosome appear more often in males?
because there is no corresponding allele on the Y chromosome to mask them
What is haemophilia?
a disorder caused by a recessive X-linked allele
Who do males always inherit the X chromosome from?
Mother
Who can affected fathers pass haemophilia to?
Daughters
What are autosomes?
Chromosomes that don’t determine the sex of an organism
What is the effect of autosomal linkage on inheritance?
it results in a non-random association of alleles at different loci
How does autosomal linkage affect genetic variation in offspring?
it decreases genetic variation by producing a low number of recombinant offspring
What is the term for offspring that have different combinations of alleles from their parents due to crossing over?
Recombinant
What is a multiple alleles cross?
When a gene has more than two alleles, they are a type of codominance, e.g. blood type A, O, and B
What is epistasis?
an interaction between genes where one gene affects or masks the expression of another gene
In the context of epistasis what does the term masking mean?
the process of one gene hiding the effects of another gene
What is the term for a gene whose expression is blocked by another gene?
Hypostatic
What is the chi squared test used for?
The chi squared test is used to compare the goodness of fit of observed phenotypic ratios with expected ratios.
How would you calculate the degrees of freedom for a chi-squared test in genetics?
the number of phenotypes minus one
What should you do if the chi-squared statistic is greater than the critical value at the chosen probability level?
reject the null hypothesis
What does it mean if the chi-squared statistic is less than the critical value at the chosen probability level?
the differences between the observed and expected frequencies are due to chance
