Lecture 2: Mutation, Variation and genome organisation Flashcards Preview

APS125 Genes in Populations > Lecture 2: Mutation, Variation and genome organisation > Flashcards

Flashcards in Lecture 2: Mutation, Variation and genome organisation Deck (46):
1

What are mutation?

-the failure to store genetic information faithfully.
-affect whole chromosome or single genes
-spontaneous or induced
-harmful, neutral or beneficial
-the source of ALL genetic variation
-necessary for natural selection and evolution

2

Causes of mutation.:

induced mutations- radiation, UV, X-rays. Anything that increases chemical reactivity in the cells - MUTAGEN
e.g. Chernobyl 1986
Fukushima 2011

3

Karyotype..

is simply a picture of a person's chromosomes

4

Humans chromosomes are present in..

pairs they're diploid.
23 pairs, 2n = 46

5

Gametic cells are

(egg and sperm)
haploid!

6

Chromosomal variation:

-Polyploidy
-Aneuploidy
-Translocations
-Deletions
-Inversions

7

Polyploidy:

cells and organisms are those containing more than two paired (homologous) sets of chromosomes.

8

Bacteria are usually...Diploid, monoploid or dispermy?

MONOPLOID

9

If greater than 2 sets of chromosomes i.e. dispermy

results in 3 complete sets of chromosomes; 3n = 69.
Happens in 1-3% of conceptions - ALWAYS LETHAL .

10

Dispermy-

fertilisation of one egg by two sperm

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Polyploidy in higher plants is

common. Related species often vary in ploidy.

12

Aneuploidy is when

one set of chromosomes is incomplete. e.g. a chromosome is missing, an extra chromosome is present

13

Autosome..

any chromosome that is not a sex chromosome

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Nullisomy:

Autosomes when both members of a pair are missing - lethal

15

Monosomy:

Autosomes when one member of a pair is missing - lethal

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Trisomy:

Autosomes when one extra chromosome; usually lethal

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Trisomy 21 -

Down syndrome.
Longevity = 40+ not considered lethal

18

Aneuploidy in sex chromomses..

Lacking a chromosome:
45X - Turner's syndrome
45Y - Inviable
Extra chromosomes: 47XYY, 47XXY, 47XXX Minor effects

19

Translocations:

Exchange of parts between NON-HOMOLOGOUS chromosomes

20

Homologous chromosomes..

=chromosomes that contain alleles for the same gene

21

Translocation;
carriers and offspring

carriers are normal
Offspring can have the wrong number of copies of each chromosome - usually lethal

22

Deletions:and example

-Part of a chromosome is missing
-Patient only has one copy of each gene in that region
-severity depends on size of missing region
-chromosome 5, Cri-du-chat syndrome

23

Inversions:

Breakpoints in chromosome appear. Middle section is inverted.
say: ABCDEFGHI
ABC|DEF|GHI
ABCFEDGHI
Often no effect on phenotype- a balanced rearrangement.
Possible problem in meiosis

24

Meiosis...

type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells

25

Structure of DNA:

-sugar phosphate backbone
-polymer made up of units called nucleotides
-bases held together by H-bonds
-Adenine
-Thymine
-Guanine
-Cytosine
-AT & CG
(in RNA T swaps to U)

26

DNA is a

Double helix

27

Size of the human genome...

3X10^9 (3 billion) base pairs long

28

Cricks second great discovery :

The genetic code.
Where 3 nucleotides are called a codon
Every codon specifies one amino acid
An amino acid can be encoded by more than one codon - the code is DEGENERATE

29

Organisation of the human genome:

-20-300 genes
-only 1.5% encodes for proteins
-~3% regulates protein expression
-~ 45% caused by transposons
-~6.6% not transcribed
-~44% Contains many useful variations

30

DNA mutations: coding region mutations..

-substitutions
-insertions and deletions

31

DNA mutations: Non-coding region mutations..

-repeat length variation
-Useful genetic markers

32

Substitution Mutation...

CAT<> CAC
Can be silent (synonymous mutation) or replacement mutation (non-synonymous) depending on where the substitution occurs

33

Insertion/ deletion (indels) mutation...

Result is different protein encoded due to a shift in the open reading frame

34

Non- coding region mutation:
% of genome not involved in protein coding/expressio?..
Variation in these parts is..

95%
Very useful!
Single Nucleotide Polymorphisms (SNPs)

35

How many SNPs are found in man?

12,000,000 - 0.3% of genome

36

What is an SNP?

a variation in a single nucleotide that occurs at a specific position in the genome, where each variation is present to some appreciable degree within a population

37

Satellite DNA..

Micro satellites (or simple tandem repeats). Nearly always harmless. Widely used in finding diseases, conservation genetics, evolutionary genetics, agricultural improvement

38

Gametic mutations:
Heritable?
Effect?
Affect all cells?

Heritable? YES
Effect? Can be severe
Affects all cells? YES

39

Somatic mutations:
Heritable?
Effect?
Affect all cells?

Heritable? NO
Effect? Usually mild
Affects all cells? NO

40

Genetic variation is caused by...

MUTATION

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there would be no evolution without

MUTATIONS

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Mutations can affect

Chromosomes or nucleotides

43

Chromosomal mutations are often..

Lethal

44

The genetic code is...

Degenerate

45

Nucleotide mutation scan occur in ..

Coding or non-coding regions

46

Gametic mutations are,,

inherited