Genes, Chromosomes and Heredity Flashcards
Define clone
an organism or cell, or group of organisms or cells, produced asexually from one ancestor or stock, to which they are genetically identical
Define homologous chromosomes
chromosomes that synapse or pair during meiosis and that are identical with respect to their genetic loci and centromere placement
Define dihybrid cross
a genetic cross involving two characters in which the parents possess different forms of each character (e.g. yellow, round X green, wrinkled peas)
Define missense mutation
a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid
Define complementary gene action
one of two or more genes that when present together produce effects qualitatively distinct from the separate effect of any one of them.
Define null mutation
A mutation (a change) in a gene that leads to its not being transcribed into RNA and/or translated into a functional protein product
___________ are the source of genetic variation, the raw material of evolution. They are needed for species to adapt
Mutations
Define molecular genetics
the field of biology that studies the structure and function of genes at a molecular level and thus employs methods of both molecular biology and genetics
What is the term used to describe when there is multiple allels equavalent to wild type?
Polymorphic
What is typical of a pedigree displaying an autosomal recessive trait?
- Males and females equally affected
- Skips generations
What does a mutation in the splice site do?
pre-mRNA may not be spliced correctly- could have a similar result to a frameshift mutation
True or False:
Complementary gene action is a type of epistasis
True
Define suppressor gene
a gene that suppresses the phenotypic expression of another gene
Define homozygote
an individual with identical alleles for a gene or genes of interest. These individuals will produce identical gametes (with respect to the gene or genes in questions) and will therefore breed true
Define penetrance
the frequency, expressed as a percentage, with which individuals of a given genotype manifest at least some degree of a specific mutant phenotype associated with a trait
What is the term used to describe when there is one wild type allele and the rest is mutant?
Monomorphic
Define codominance
condition in which the phenotypic effect of a gene’s alleles are fully and simultaneously expressed in the heterozygote
Define reciprocal cross
a pair of crosses in which the genotypes of the female is present as the genotype of the male in the other, and vice versa
Define dominant epistasis
when the dominant allele of one gene masks the effects of either allele of the second gene
Duchenne muscular dystrophy is an X-linked recessive disorder.
- If a woman who is a carrier of the disease gene has a normal partner what is the probability of having an affected child?
Define autosomal
a gene located on a numbered chromosome and usually. affects males and females in the same way
Define mutagen
an agent, such as radiation or a chemical substance, which causes genetic mutation
True or False:
Suppressor alleles are always dominant
False
They can be dominant or recessive
A ratio of 13:3 is typical of which type of gene interaction?
Recessive suppression
Define pedigree
in human genetics, a diagram showing the ancestral relationships and transmission of genetic traits over several generations in a family
What is typical of a pedigree displaying an autosomal dominant trait?
- Males and females equally affected
- Affected individuals in multiple generations
- Transmission by both sexes to both sexes
Define testcross
a cross between an individual whose genotype at one or more loci may be unknown and an individual who is homozygous recessive for the gene or genes in question
What type of inheritance does this pedigree show?
Sex influenced
Define incomplete penetrance
A form of penetrance in which not all individuals carrying a deleterious gene express the associated trait or condition
What is it called when an individual only has one copy of a gene?
Hemizygous
Define transmission genetics
the field of genetics concerned with heredity and the mechanics by which genes are transferred from parent to offspring
Define population genetics
the branch of genetics concerned with the hereditary makeup of populations
Define Mendel’s Law of Independent Assortment
Mendel’s second law that states that alleles for separate traits are passed independently of one another i.e from parents to offspring
Define allele
one of the possible alternative forms of a gene, often distinguished from other alleles by phenotypic effects
Define recessive
an allele whose potential phenotypic expression is overridden in the heterozygous condition by a dominant allele
Duchenne muscular dystrophy is an X-linked recessive disorder.
- What is the probabilty that a woman whose mother’s brother had the disease will have received the disease allele?
What type of inheritance does this pedigree show?
Autosomal recessive
What type of inheritance does this pedigree display?
X-linked recessive
Define monohybrid cross
a genetic cross involving only one character (e.g. AA X aa)
Define phenotype
the overt appearance of a genetically controlled trait
A certain type of flower can be purple (dominant) or white (recessive). You find a purple flower and want to determine what it’s genotype is.
a) What test do you perform?
b) What flower would you cross it with?
c) What do you expect if the genotype is PP?
d) What do you expect if the genotype is Pp?
a) Test cross
b) White flower
c) All purple flowers
d) 1:1 ratio (purple:white)
When organisms homozygous for mutations that show the same phenotype but are in different genes are crossed together, then the progeny are wild type. The mutations __________ one another
Complement
Cystic fibrosis is an autosomal recessive disorder. Two heterozygous parents are expecting a baby.
- What is the probability that the baby is a homozygote?
CC or cc
1/4 + 1/4 = 1/2
What sort of gene interaction does a ratio of 9:3:4 indicate?
Recessive epistasis
Define carrier
an individual heterozygous for a recessive trait
Is loss-of-function mutations usually dominant or recessive?
Recessive
Define loss-of-function
A mutation that results in reduced or abolished protein function
What is typical of a pedigree displaying an X-linked recessive trait?
- Males usually mostly affected
- Transmitted through unaffected females (carriers)
- No male to male transmission
Cystic fibrosis is an autosomal recessive disorder. Two heterozygous parents are expecting a baby.
- What is the probability that the baby is affected?
Cystic fibrosis is an autosomal recessive disorder. Two heterozygous parents are expecting a baby.
- What is the probability that they have a baby that is affected and then have a second baby who is unaffected?
Which trait in this monohybrid cross is dominant and which is recessive?
Round = dominant
Wrinkled = recessive
If we have two mutations with the same phenotype, we can test if they are affecting the same gene, or different genes using a _____________
Complementation test
Define splice site
the specific site at which splicing takes place during the processing of precursor messenger RNA into mature messenger RNA
Define conditional mutation
a mutation that has wild-type (or less severe) phenotype under certain “permissive” environmental conditions and a mutant phenotype under certain “restrictive” conditions
What type of inheritance is suspected when an allele appears to be dominant in one sex and recessive in another?
Sex-influenced
An allele of one gene that reverses the effect of a mutation of another gene, resulting in a wild-type phenotype is called what?
Suppressor allele
Define duplicate recessive epistasis
When recessive alleles at either of the two loci can mask the expression of dominant alleles at the two loci
What ratio is expected when two genes affect different traits?
9:3:3:1