Lecture 2: DNA Damage and Repair, Mutation and Resulting types of Genetic Variation

Genome

the dna content of the organism

types of dna damage

spontaneous

induced

spontaneous dna damage

errors in replication:

• dna polymerase adds incorrect base during replication

• there is misalignment during replication

chemical changes in DNA

induced dna damage via environment

chemical mutagens

• mutagen inserts itself into dna

• Mutagen is chemically similar to og base an

radiation

mutation

is a change in DNA that is transmitted through cell division

Most spontaneous or induced damages to DNA can be repaired before it is inheritedacross cell division

True

Types of genome mutations

insertion

substitution

deletion

point mutations

insertion mutation

when one bases is added to DNA sequence

ex: goes from 9 to 10 bases

substitution mutation

when one bases replaces another

ex: a gets changed to c

deletion mutation

when one bases is removed from dna sequence

ex: goes from 9 to 8 bases

point mutations

mutations that alter a single base

t/f: insertion/deletion mutations can vary in scale from single-base to chromsomal

chromosom

true

Trio study about mutations summary

• a dipolid baby has about 60 new point mutations

• every site in genome can and does mutate

• chances of base mutating are very low 1/100,000,000 per generation

t/f: mutation happen randomly without a selective effect

true

which way is mRNA written:

5’ to 3’

haplotype

DNA sequence from a single chromosome that is usually inherited together

single-nucleotide polymorphism (SNP)

a variable sit as a result from a point mutation

locus

location on a chromosome

allele

different DNA sequence alternative at a locus

Most SNPs occur in gene coding region of dna

false: most of them occur in the non coding regions of genome

genes

coding regions of the genome because they contain sequence that encode proteins

intron

DNA in geen that is splice out of mRNA before translation

exon

DNA in gene that become remains to become mRNA

t/f: genetic code is the same as genetic sequence

false: the entire geneome is made up of genetic sequence but only a little part of it codes

genetic code

the list of codons that correspond to a particular amino acid

t/f: majority of mutations occur in non codiing regions and have no consequence at the protein level

true

t/f: all of life shares building blocks of proteins: amino acids

true

proteins

made up of folded amino acid chains that are the building blocks of biological function

t/f: outcomes of Mutations at different points in the coding region are different

true: bc genetic code is redundant, so multiple, codons can make the same amino acid

it depends on the loction of coding region/amino acid sequence

nonsynonymous mutations

changes of of amino acid that result in change in protein structure/phenotype

ex: amino acid codon changed to stop codon

changes in codon: GGA to AGA

t/f: base substitution in a regulatory region will result in alterations at the transcription level

true: promoters are dont code for proteins but they are important for initiation of transcription

t/f: in/del mutations, even those caused by transposable elements, are common causes of genome variation

true

t/f: mutations in somatic cells are heritable>

falses: they are only passed down to clones of those cells within the body but not gen.

t/f: mutations in germline are heritable

true

t/f: most mutations will no affect biological function

true: 90% of the human genome is relevant to biological functions and most mutations occur in the noncoding regions of the genome

DNA damage becomes. a mutation when it is not repaired

true

Lederberg experiment

• used replica plating with E. coli and bacteriophage T1.

• They tested whether the virus caused bacteria to mutate into resistant forms.

• The same resistant colonies appeared in corresponding positions on multiple replica plates.

• This showed that resistant mutations had already occurred randomly during cell division, before virus exposure.

• The virus did not cause bacteria to develop a mutation; it just selected for the bacteria that were already resistant

• Showed that mutations are random with respect to the environment

genetic markers

DNA sequence variations that cna be used to tracj inheritance of different parts of chromosome in the offspring of genetic crosses

t/f: all genetic markers have a phenotypic effect

false: most genetic variation is not relevant to biological function