1 The Human Genome Flashcards

1
Q

What does genome consist of

A

All DNA in a cell - includes introns and exons

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2
Q

What is an exon in DNA

A

Section that codes for proteins

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3
Q

How many nucleotides are there in the human genome

A

3 x 10^9

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4
Q

How many autosomes do humans have

A

44

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5
Q

How many sex chromosomes do humans have

A

2

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6
Q

Which cells doesn’t have a nucleus and why

A

RBC- increases O2 capacity and can squeeze through capillaries
Platelets

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7
Q

What is Synteny

A

When genes are present in the same order across species

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8
Q

What is a Barr body

A

In inactive X chromosome

Women inactivate one copy of thier X chromosome and push it to the edge of the nucleus

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9
Q

How many chromosomes do chimps and gorillas have

A

48 chromosomes

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10
Q

What is human chromosome number 2 a fusion of?

A

Two chimp/ gorilla chromosomes

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11
Q

What is Translocation and what can it cause

A

When chromosome segments change location

  • break off and reattach to a new chromosome
  • can cause disease and cancer
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12
Q

Give examples of cells which can copy DNA by dividing the nucleus but not entire cell

A

Hepatocytes

Megakaryocytes

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13
Q

Translocation in chromosome 9 and 22 = Philadelphia chromosome leads to what type of cancer

A

Chronic myelogenous leukaemia = bone marrow produces too many myeloid cells that aren’t fully myeloid cells that are not fully developed

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14
Q

What are the two types of regularity RNAs

A

MRNA AND Xist

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15
Q

What are they two types of structural RNAs

A

RRNA tRNA

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16
Q

What is Xist

A

X inactivation Specific Transcript

In XX cells one copy of X chromosome is switched off

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17
Q

What does Xist do

A

Binds to X chromosome in females which condenses and inactivates them so women only receive info from one chromosome

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18
Q

Maimoona is the best

A

Yayyy

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19
Q

What does each end of mRNA contain

A

Untranslated regions UTR
5’ UTR= important for regulation of translation
3’ UTR= section of mRNA that immediately follows translation termination codon

20
Q

What are gene deserts

A

Large non-coding (intergenic) regions

21
Q

Genomic imprinting

A

Allows genes to be expressed differently depending on which parents they come from

22
Q

What is the result of imprinting in diploid organisms

A

One of two alleles is silenced

23
Q

Which two ways can genes be silenced by

A

DNA methylation or histone modification

24
Q

Retrovirus

A

RNA viruses that insert their DNA into the DNA of host cells

25
Q

Give an example of a retrovirus

A

HIV

26
Q

How much space does mutated retrovirus take up in our DNA compared to exons

A

Twice as much

27
Q

What is a pseudo gene

A

An allele of normal genes that have become non functional due to mutations.

28
Q

Give an example of how pseudo genes might be generated

A

Gene duplication - if genes are inserted unintentionally it becomes a non functional gene - no protein
Or
Protein codon region may contain stop codon = non functional protein

29
Q

Why are stop codons also pseudogenes

A

They lack protein-coding ability

30
Q

What are VNTRs

A

Variable number tendon regions - multiple copies of short sequences

31
Q

What is slippage caused by and what can it cause

A

Caused by insertion of two many or too few copies

Leads to disease

32
Q

Give an example of a disease caused by slippage of replication of repeat sequence

A

Huntington’s disease

33
Q

What is Huntington’s disease caused by

A

Expansion of CAG repeat in Huntington protein gene- causes Neuron degeneration

34
Q

Symptoms of Huntington’s disease

A

Death of neurons - affects balance movement, talking breathing etc

35
Q

What is a telomere and what is their function

A

Repeat sequence in a genome

Protects the end of chromosomes from deterioration/ fusion with neighbouring chromosomes

36
Q

What is the repeat sequence of a telomere

A

TTAGGG

37
Q

Which enzyme builds telomeres

A

Telomerase

38
Q

Which cells switch on telomerase

A

Stem cells

39
Q

Which cells switch off telomerase

A

Differentiated cells

40
Q

Another function of telomeres

A

Regulate number of cell divisions

41
Q

What is cell senescence

A

When it can no longer divide/ Inactive

42
Q

What effect do cancer cells have on telomerase

A

Increase telomerase, adding more repeat sequences so cells can continuously divide

43
Q

What is a SNP single nucleotide polymorphism

A

DNA sequence variation occurring commonly within a

population (e.g. 1%) in which a single nucleotide in genome differs between members of species

44
Q

What effect do SNPs have on ANRIL

A

) increases risk of heart disease &

diabetes

45
Q

Do all SNPs cause changes in phenotype

A

Some do but some are silent