Lecture 9 Flashcards Preview

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Flashcards in Lecture 9 Deck (40):
1

What are the 2 type of chromosomal mutations

structural and number

2

Changes in chromosomal number are refereed to as

polyploid changes

3

Structural mutations involve

novel sequence rearrangements within 1 or more DNA molecule

4

Why are chromosomal mutations important x5

- understand how genes work together
-insights into meiosis and chromosome architecture
-tools for genomic manipulation
-cause of genetic diseases
-insights into evolutionary processes

5

Types of chromosomal mutations x3

-loss of genetic material
-gain of genetic material
-relocation of genetic material

6

What causes loss of genetic material (x2)

-deletion
-missing chromosome

7

what causes a gain in genetic material (x2)

-duplication
-extra chromosome

8

What causes relocation of genetic material (x2)

-Translocation
-inversion

9

How do you form a deletion?

A chromosome segment can be lost

10

How do you form a duplication?

a section can be doubled

11

What sort of breaks are lethal unless repaired, and how can chromosomal rearrangement result from this

Double-stranded breaks; If ends of 2 different breaks are joined a chromosomal rearrangement can result

12

What does a DNA molecule have to have to survive meiosts

-Centromere
-2 telomeres

13

What is nonallelic homologous recombination

Crossing over between duplicated DNA sequences (this causes rearrangements)

14

How can crossing over occur between non-homologous chromosomes

Repeat sequences on different chromosomes (or within 1 chromosome)

15

If crossing over occurs between repeat DNA sequences that are not if in the same position on homologs then what can be produced?

-Deletions
-Duplications
-inversions
-translocations

16

Why is a deleted segment often lost?

Because it has no centromere

17

What's a terminal deletion

Segment deleted at the end of a chromosome

18

What's a interstitial deletion

segment deleted within a chromosome

19

Intragenic deletion

a small deletion within a gene that inactivates the gene

20

Multigenic deletions

Involve several genes and their consequences are more severe

21

When is a loop formed by a chromosome

In meiosis the chromosome of a deletion heterozygote

22

What are the consequences when a multigenic deletion is made homozyous by inbreeding

Lethal consequences

23

What sort of mutations never revert back to the wildtype

Multigenic mutations

24

Pseudodominance (to do with deletions)

Deletions allow the expression of phenotypes carried as recessive alleles

25

Tandem duplications

Duplications that are adjacent

26

Insertional duplications

Duplications that are located elsewhere (not adjacent) in the genome

27

If a duplication has occured, how many copies of that chromosome region will a diploid cell have

Three copies

28

What does detection of duplications involve?

Looking for duplications of chromosome banding patterns + the presence of loops at meiosis in heterozygous individuals

29

Describe the Bar mutation (4 main points)

-Mutation in Drosophila
-that have reduced facests in the eye, making the eye smaller
-the trait is inherited as an incomplete or partial dominant X linked train
-Heterozygous females have smaller eyes, while even smaller is that of homozygous females and hemizygous males
(see image in slides)

30

Segmental duplications

Duplications that range in size from 10-50 kbp and encompass whole genes and the regions between them.
-Most segemental duplications are dispersed but some are tandem.
-About 4% of the genome consists of segmental duplications

31

Paracentric Inversions

The centromere will be outside the inversion

32

Pericentric inversions

The centromere is inside the inversion

33

Are people with inversions usually normal or not?

Yes because inversions dont change the overall amount of genetic material

34

Para or peri centric inversions cause the formation of a dicentric bridge

Paracentric

35

What's an inversion loop

During meiosis 1 chromosome twists at the ends of the inversions so that it can pair withe the untwisted homolog

36

In para or peri centric inversions does an acentric fragment form

paracentric - this fragment is lost because it has no centromere

37

In para or pericentric inversions can crossing over result in duplications and deletions result

Pericentric

38

Explain what it is meant by: Inversions act as crossover supressors

They dont stop crossing over happening, you just dont see any crossover product as they are not viable

39

Explain what it is meant by: Inversions can lead to the creation of 'Super Genes'

Gene are linked, can not be broken up as no crossing over

40

What is often detected when patients are having fertility problems

Paracentric or pericentric inverisons