MCB Lecture 18 Intro to genes Flashcards Preview

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Flashcards in MCB Lecture 18 Intro to genes Deck (31)
0

What is the major functional division of the genome?

Unique sequences

Intergenic sequences

1

What are the two categories in unique sequences?

Genes

Related sequences

2

What is a gene?

A gene is a sequence of DNA that codes for a protein or a functional RNA

3

Differentiate between the coding and the template strand

Coding strand is identical to the mRNA

Template strand is the one read by the RNApol and is thus complimentary to the mRNA

4

What are related sequences?

UTRs, introns, exons

Pseudo genes

Gene fragments

5

What are introns, exons and UTRs?

Introns: Intervening sequences. These interrupt the gene, are spliced out after transcription to form the mature mRNA
Exons: Expressed sequences. The parts that make up the mature mRNA

UTRs: regions between the 5' cap and the start of the gene and the end of the gene and the poly-A tail that are not translated

6

What is the average number of introns in a gene?

10

7

What are gene fragments?

This is when a part of the gene is separated from the rest and is no longer functional

8

What are pseudo genes?
What are the two types? Differentiate between the two

Pseudo genes look like genes, but have changed to become non-functional

Processed: mRNA has been reverse transcribed back into the genome. The introns are thus missing

Conventional: accumulation of mutation

9

What is example of a pseudo gene?

Beta globin genes

10

What are the two categories in 'intergenic sequences'?

Interspersed

Non-interspersed

11

What are the four categories in 'interspersed intergenic sequences?

LINEs
SINEs
LTR
Transposons

12

What are retrotransposons?
How do these move around the genome?

LINEs
SINEs
LTRs

These are transcribed from the gene to give mRNA.
Then, reverse transcriptase transcribes them back into DNA, and they insert in some other place in the genome

13

What are DNA transposons?
What are the two mechanisms for moving around the genome?

DNA transposons do not go through a mRNA intermediate: they are inserted directly into some other region of the genome.

Conserved: transposase enzymes bind at the ends of the gene, cleaves the phosphodiester bonds, and forms a loop. It then inserts it somewhere else

Replicative: sequence is copied directly into DNA and the copy inserts somewhere else

14

What are SINEs?

Short interspersed repeats

15

What are LINEs?

Long interspersed repeats

16

What are micro satellites?

How many base pairs per repeat?

Micro satellites are an array of short tandem repeats

Each repeat is 2-6 base pairs

17

What are mini satellites?

How many base pairs per repeat?

Mini satellites are an array of long tandem repeats

Each repeat is 10-60 bp

18

What are telomeres?

These are repeated regions at the end of a chromosome that prevent important regions from being cut off when during DNA replication

19

What are centromeres?

These are repeated regions whose function is to form the structure of the centromere

20

Describe the packing of chromosomes

Nucleosomes, coiling and super coiling to form chromosomes

21

Talk about variation in size of genomes

Different species have different sized genomes.

Smaller the organism, smaller the genome generally, but does not always hold. Eg. Locusts

22

Talk about gene density

This is number of genes per amount of DNA

Humans have very low gene density

23

What are LTRs?

Long terminal repeats

These are a type of interspersed repeat
Retrotransposon

24

What is a tandem repeat?

End to end repetition of DNA sequence at a defined locus

25

What are STRs and SSRs?

Short tandem repeats and Simple sequence repeats.

These are just other names for micro satellites

26

Which sort of repeat is much used for DNA profiling/fingerprinting?

Micro satellites

27

What are replication origins?

Important, but non coding element in the DNA where replication begins

28

Half of the molecular mass of eukaryotic chromosomes is ...

Protein; the histones.

29

Describe the structure of histones

Core octamer of:
2 x H2A
2 x H2B
2 x H3
2 x H4

30

Way is the function of histones?

- Packs the DNA up neatly in the cell
- Decreases the accessibility of the DNA --> exploited for regulation

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