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Miscellaneous > MCB Lecture 18 Intro to genes > Flashcards

MCB Lecture 18 Intro to genes Flashcards

0
Q

What are the two categories in unique sequences?

A

Genes

Related sequences

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1
Q

What is the major functional division of the genome?

A

Unique sequences

Intergenic sequences

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2
Q

What is a gene?

A

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

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3
Q

Differentiate between the coding and the template strand

A

Coding strand is identical to the mRNA

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

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4
Q

What are related sequences?

A

UTRs, introns, exons

Pseudo genes

Gene fragments

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5
Q

What are introns, exons and UTRs?

A

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

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6
Q

What is the average number of introns in a gene?

A

10

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7
Q

What are gene fragments?

A

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

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8
Q

What are pseudo genes?

What are the two types? Differentiate between the two

A

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

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9
Q

What is example of a pseudo gene?

A

Beta globin genes

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10
Q

What are the two categories in ‘intergenic sequences’?

A

Interspersed

Non-interspersed

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11
Q

What are the four categories in ‘interspersed intergenic sequences?

A

LINEs
SINEs
LTR
Transposons

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12
Q

What are retrotransposons?

How do these move around the genome?

A

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

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13
Q

What are DNA transposons?

What are the two mechanisms for moving around the genome?

A

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

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14
Q

What are SINEs?

A

Short interspersed repeats

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15
Q

What are LINEs?

A

Long interspersed repeats

16
Q

What are micro satellites?

How many base pairs per repeat?

A

Micro satellites are an array of short tandem repeats

Each repeat is 2-6 base pairs

17
Q

What are mini satellites?

How many base pairs per repeat?

A

Mini satellites are an array of long tandem repeats

Each repeat is 10-60 bp

18
Q

What are telomeres?

A

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

19
Q

What are centromeres?

A

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

20
Q

Describe the packing of chromosomes

A

Nucleosomes, coiling and super coiling to form chromosomes

21
Q

Talk about variation in size of genomes

A

Different species have different sized genomes.

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

22
Q

Talk about gene density

A

This is number of genes per amount of DNA

Humans have very low gene density

23
Q

What are LTRs?

A

Long terminal repeats

These are a type of interspersed repeat
Retrotransposon

24
Q

What is a tandem repeat?

A

End to end repetition of DNA sequence at a defined locus

25
Q

What are STRs and SSRs?

A

Short tandem repeats and Simple sequence repeats.

These are just other names for micro satellites

26
Q

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

A

Micro satellites

27
Q

What are replication origins?

A

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

28
Q

Half of the molecular mass of eukaryotic chromosomes is …

A

Protein; the histones.

29
Q

Describe the structure of histones

A 
Core octamer of:
2 x H2A
2 x H2B
2 x H3
2 x H4
30
Q

Way is the function of histones?

A
  • Packs the DNA up neatly in the cell

- Decreases the accessibility of the DNA –> exploited for regulation

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