3.7.1 Inheritance Flashcards
What is the genotype?
All the alleles that an organism has
What is the phenotype?
The observable or biochemical characteristics of an organism
What is a gene?
A length of DNA which is a sequence of nucleotide bases
What is an allele?
One of the different forms of a gene
What is the locus?
The position of a gene on a particular DNA molecule
What are homologous chromosomes?
Chromosomes in pairs with the same gene loci
What are homozygous alleles?
When both alleles are the same
What are heterozygous alleles?
When the alleles are different
What is a dominant allele?
One that is expressed
What is a recessive allele?
One that is not expressed
What is it called when a homozygous organism has two dominant alleles?
Homozygous dominant
What is it called when a homozygous organism has two recessive alleles?
Homozygous recessive
Define codominant alleles
When both alleles contribute to the phenotype. This can either be a blend of features or when both features are represented
What is it called when an organism is said to have multiple alleles?
When a gene has more than two allelic forms
What is a Punnett square?
A cross diagram used to show the genes of genetic offspring
What are pure breeding strains?
When alleles are the same
What is the generation called if it is a cross between two pure breeding parents?
First filial or F1 generation
What is the generation called when an F1 generation is crossed with another F1 generation?
Second filial or F2 generation
What is dihybrid inheritance?
How two characteristics, determined by two different genes located on different chromosomes, are inherited
How many chromosomes do humans have?
23 pairs
Define sex-linked
When a gene is carried on the X or Y sex chromosome
Which sex chromosome is longer?
X
So most of the X chromosome don’t have an equivalent homologous portion
Those non-homologous chromosomes have no pairing so will always be expressed
What is an X-linked genetic disorder?
A disorder caused by a defective gene on the X chromosome
How is a sex linked allele represented?
X or Y to the power of (letter respresenting the allele)
Why do males always inherit an X-linked genetic disorder from their mothers?
They have to get their Y chromosome from their father so the X chromosome must be from the mother
What are the sex chromosomes for males and females?
XX for females
XY for males
What is a carrier?
A person who has an allele of a disease without displaying the physical symptoms
What is a pedigree chart?
A chart which shows the inheritance of sex-linked characters in a family
A male is represented as a square
A male is represented by a circle
Shading indicates the presence of a character in the phenotype
What are autosomes?
The chromosomes which aren’t sex chromosomes
Define linked genes
When two genes occur on the same chromosome
What forms a linkage group?
All the genes on a single chromosome
What is the name of the situation where two or more genes are carried on the same autosome?
Autosomal linkage
Draw a diagram of non-linked genes
See card
Draw a diagram of linked genes?
See card
Does independent selection affect autosomal linkage?
No
How do you complete the chi squared test?
Columns: category, observed number (O) , expected number (E) , O - E, (O - E)2, (O - E)2 / E
X2 = Sum of: (O - E)2 / E
How do you evaluate the value calculated in the chi squared test?
If your calculated value is less than the degree of freedom, accept the null hypothesis that there is a significant difference between your observed and expected results
If the value is larger than the degree of freedom, there is epistasis or linkage of the alleles
What is epistasis?
When the allele of one gene affects or masks the expression of another in the phenotype
How do you use the word epistatic?
If one gene locus prevents the expression of a second gene, the first locus is epistatic to the second and the second is hypostatic to the first
