Seminar 14: Genetic variation Flashcards
(27 cards)
desc somatic mutations
mutations w/in body cells, aren’t passed onto offspring
desc germline mutations
- mutations that occur w/in reproductive cells (egg, sperm)
- passed onto offspring (may or may not inherit them)
desc de novo mutations
- genetic changes that appear spontaneously in an individual’s DNA
- they were not inherited from either parent
- Can occur in germline or somatic cells
- Can arise during formation of sperm/egg or after fertilisation
desc induced mutation
- Occur due to external factors (Mutagens)
- e.x mutagens: Radiation, chemical, certain drugs/substances
desc spontaneous mutations & give an ex
- Occur without any outside influence
- E.x: Deamination, removal of NH2 grp from a nucleotide, cytosine > uracil,
- E.x: Transposon, able to move from 1 position to another in the genome (transposition)
what factors induce DNA damages?
- Heat
- Radiation
- Oxidation (by free radicals prod in cellular resp)
Hydrolytic reactions are _____ DNA damage caused by ___
Spontaneous DNA damage caused by H2O
what does Deamination affect, & what does it cause
affects PYRIMIDINES (C, T), loss of NH2 in presence of H2O that converts it to Uracil
what does Depurination affect, & what does it cause
affects PURINES (A, G), cleavage of bond b/w base & deoxyribose (loss of purine), leaves Apurinic site in DNA
How does the structure of DNA support accuracy of DNA repair mechanisms?
Double stranded (suitable for repair)
- 2 separate copies of genetic info in 2 strands: if 1 strand is damaged, the other can be used to restore the correct seq
SYNONYMOUS/SILENT MUTATION are
- Changes in DNA seq that DOESN’T ALTER A.A SEQ
- Change in 1 nucleotide of a codon, but the codon still codes for the same A.A
- E.x UUA > UUG = leucine
NONSYNONYMOUS MUTATION are
Nucleotide substitution results in change of A.A seq encoded by the gene
(missense & nonsense)
Missense mutation
AA substitution due to change in 1 nucleotide
Nonsense mutation
PP chain shortened prematurely because codon is changed to a STOP CODON
types of LARGE mutation (3)
- Gene duplication - entire gene copied
- Inversion - change orientation of chromosomal region
- Genome duplication - double # of chromosomes in an indv
FRAMESHIFT MUTATION are
- cause diff PP chain to be prod
- mRNA codons read differently, dysfunctional protein
Copy Number Variations (CNV) are
- diff in the # of copies of specific DNA sequences w/in a genome, compared to a reference genome
- structural variations involving DNA segments of more than 1 kilobase pair
mutations to CNVs
- Can decrease copy #: by deletion, result in null genotype
- Can ^ copy # of gene : duplication & insertion
- CNV can affect phenotypes that are dependent on # of func gene copies
SNPs are
- Single Nucleotide Polymorphism
- random, single base substitutions found throughout the genome
desc SNP mutations
- Once every 1,000 nucleotide
- SNP if its found in more than 1% of pop
- Can confer diseases e.x diabetes, cancer
what are alleles
- diff forms of the SAME gene
- Arise by mutation, found in same area
HOMOZYGOUS
2 copies of SAME allele
HETEROZYGOUS
2 copies of DIFF allele
HEMIZYGOUS
condition where an individual only has 1 copy of a gene instead of the usual 2
- Males have only 1 allele for X chromosome
