Chapter 4 - Variation and mutation Flashcards
Phenotype
The observable form taken by a specific feature in an individual, based on genotype and influenced by environment
Heredity
The transmission of traits from one generation to the next
Variation
The diversity of genetic and phenotypic traits within and between populations
Genotype
The genetic composition of an organism for a particular trait
what are internal and external environmental factors
- External: temperature, pH, food availability. Eg, for crocodiles an embryo can become female or male depending on temperatures in the egg. Soil pH can affect flower colour in hydrangeas
- Internal: actions of hormones. Eg, Gonadotropin releasing hormone triggering the start of puberty in humans
How can epigenetics affect phenotype, give example
By controlling gene expression. The addition of an acetyl group to promote transcription. the addition of a methyl group to reduce transcription. This does not change DNA sequence and therefore isnt a mutation
How may mutations arise
- Spontaneously during DNA replication (spontaneous mutations)
- Induced by physical or chemical environmental factors (mutagens)
- Biological agents
how is cancer caused
Mutation in a somatic cell that accelerate the rate of cell division affecting the cell’s ability to undergo apoptosis or increase the rate of mutations within the cell
what is the difference between a mutation that produces a dominant allele and a recessive allele
Recessive mutations that lead to a loss of function can be masked if the normal copy of the gene is present, for the mutant phenotype to occur, both recessive alleles must contain the mutation. Dominant mutations lead to a mutant phenotype even in the presence of a normal copy
aneuploidy
Describes a genome that varies from the conventional genomes through loss or addition of one or a few chromosomes
Beneficial mutation
mutation that increases organisms chances of survival and reproduction
Deleterious mutation
a mutation that decreases an organisms chances of survival and reproduction
Deletion mutation
a mutation in which one or more nucleotide pairs have been lost from a segment of DNA, results in a frameshift
double strand break
a mutation involving breaks in the sugar phosphate backbones of both DNA strands at the same nucleotide pair, resulting in the complete breakage of a chromosome
Frameshift mutation
A mutation that changes the reading frame used in translation during polypeptide synthesis
Insertion mutation
a mutation in which one or more nucleotide pairs have been added to a segment of DNA. resulting in a frameshift
Missense mutation
A gene mutation that results in one amino acid being replaced by another amino acid in the encoded protein
neutral mutation
A mutation that has no effect on an organisms chanced of survival and reproduction
non disjunction
the failure of sister chromatids in mitosis or homologous chromosomes in meiosis to seperate and go to opposite poles
nonsense mutation
a mutation in which a codon for an amino acid is changed to one that codes for a stop codon, terminating translation
Point mutation
a mutation that affects a single base pair within a gene
Polyploidy
a cell or organism with a genome comprising three or more copies of each chromosome (3n, 4n, 5n)
spontaneous mutation
a mutation occurring in the absence of exposure to mutagens
substitution mutation
a mutation in which a single nucleotide is swapped for another in the original gene sequence
Synonymous mutation
a mutation in which the DNA codon for one amino acid becomes another DNA codon for the same amino acid
what are the three Substitution mutations
Synonymous mutation (silent), Missense mutation, nonsense mutation
parthenogenesis
A process in which an entire organism is a re-generated from a single egg cells
What are the three types of point mutations
Substitution, insertion, deletion
What are the four types of chromosomal mutation
Inversion, deletion, translocation, duplication
Inversion mutation
Middle piece of a chromosome falls out, rotates 180º and the rejoins. reduced fertility
Deletion chromosomal mutation
A region of a chromosome is lost, resulting in the absence of all the genes in that area.Eg williams syndrome
Translocation mutation
The region from one chromosome is aberrantly attached to another chromosome. Eg when a segment of chromosome 8 ends up within chromosome 14 (vice versa), resulting in a form of cancer
Duplication mutation
A region of a chromosome is repeated, resulting in an increase in copies of the genes in that region. Eg, genes that control different haemoglobin’s in RBC’s arise from duplications
Independent assortment
The random orientation of maternal and paternal homologous chromosomes at the equator during metaphase one
Random segregation
The phenomenon that starts during anaphase one, when the randomly lined up maternal and paternal homologous chromosomes move to opposite poles of the cell. Each gamete ends up with a random selection of maternal and paternal chromosomes
Random fertilisation
The union of a male and female gamete, both haploid, which results in a diploid zygote. Is a random as there is no way of knowing which two gametes (each genetically unique) will form a zygote
