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Year Three - Specialities > Genetics - Basic Information > Flashcards

Genetics - Basic Information Flashcards

1
Q

What is DNA?

A

It consists of two strands of nucleotide monomers that wrap around one another to form a double helix

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2
Q

What is a nucleotide monomer made up of?

A

A sugar

A base

A phosphate group

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3
Q

What are the four DNA bases?

A

Adenine

Cytosine

Guanine

Thymine

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4
Q

What is found in the centre of the DNA double helix?

A

Bases

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5
Q

What makes up the backbone of the DNA double helix?

A

Sugars

Phosphates

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6
Q

What directions do the polynucleotide chains run in relation to each other?

A

They run anti-parallel to one another, as one runs 5’ to 3’ and the other runs from 3’ to 5’

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7
Q

What are the two DNA grooves?

A

Major groove

Minor groove

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8
Q

What is the major DNA groove?

A

It occurs where the backbones are far apart

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9
Q

What is the minor DNA groove?

A

It occurs when the backbones are close together

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10
Q

How are the two polynucleotide chains linked together?

A

Complementary base-pairing

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11
Q

What are the two DNA base pairings?

A

Adenine - Thymine

Cytosine - Guanine

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12
Q

What bonds bind DNA bases together?

A

Hydrogen bonds

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13
Q

Where is DNA located in cells?

A

Nucleus

Ribsosomes - they contain their own DNA

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14
Q

How is DNA stored in the nucleus?

A

Chromsomes

Chromatins

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15
Q

What structure is found in the centres of the nucleus?

A

Nucleolus

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16
Q

What structure is located around the nucleus?

A

Nuclear envelope

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17
Q

What is the function of the nuclear envelope?

A

It consists of nuclear pores, which allows the passage of molecules into and out of the nucleus

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18
Q

What are chromosomes?

A

A single piece of DNA containing many genes, regulatory elements and other nucleotide sequences

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19
Q

What structure divides chromosomes into two sections?

A

Centromere

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20
Q

What are the two sections of a chromosome? Which section is smaller and which is larger?

A

P - smaller

Q - larger

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21
Q

What structure is contained within the centromere?

A

Kinetochore

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22
Q

What is kinetochore?

A

A protein complex that binds to microtubules

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23
Q

What is the function of kinetochore?

A

It is involved in cell division

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24
Q

Describe the process in which DNA is packaged into chromosomes

A

DNA is wrapped around histone proteins to form structures known as nucleosomes

These nucleosomes then fold up to form a chromatin fibre

These fibres then wrap around one another to form a chromosome

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25
Why is DNA wrapped around histone proteins?
DNA is negatively charged Histone proteins are positively charged This neutralises the negatively charged DNA, which means that DNA takes up less space and inactive DNA can be folded into inaccessible locations
26
What are the two types of chromatin?
Heterochromatin Euchromatin
27
What is heterochromatin?
It is highly condensed form of chromatin that contains silenced genes
28
What is euchromatin?
It is an extended form of chromatin that contains active genes
29
When are chromatins formed?
During the S phase of interphase
30
What are telomeres?
They are the caps at the end of the DNA strands that protect our chromosomes They they are repetitive sequences of DNA that code for no particular genes
31
How do telomeres protect our chromosomes?
They prevent important genes from being deleted during cell division and DNA replication
32
Describe the end problem of linear DNA replication
After DNA replication, each new DNA strand is shorter at its 5’ end than at the parental DNA’s strand’s 5’ end This produces a 3’ overhang at one end of each daughter DNA strand This means that some of our DNA on the 5’ strand is not replicated This end problem explains why the telomeres are so important in DNA replication, as they are shortened from the DNA, but the important genes aren’t
33
What is telomerase?
It is an enzyme that fills in the gaps as a result of the end problem of linear DNA replication
34
Describe how telomerase corrects the end problem of linear DNA replication
It contains a catalytic part and a built-in RNA template. It binds to the end of a chromosome to add complementary RNA bases to the 3’ end of the DNA strand Once the 3’ end of the lagging strand template is sufficiently elongated, DNA polymerase adds the complementary nucleotides to the ends of the chromosomes, allowing the ends of the chromosomes to be replicated
35
DNA is said to be semi-conservative. What does this mean?
This means that one half of each new molecule of DNA is old and the other half is new
36
Describe the process of DNA replication
The hydrogen bonds hydrogen bonds between the complementary base-pairs are broken by special proteins This allows the double helix to be unzipped The new nucleotide molecules then pair with the bases on the two DNA strands These nucleotides molecules are joined together through the enzyme DNA polymerase. This enzyme can only add new nucleotides to the 3’ end of the growing strand, as DNA is replicated in the 5’ to 3’ direction On the lagging strand, DNA polymerase joins the nucleotides into fragments, not a whole strand This means that this strand requires an additional enzyme, known as ligase, to come and join the fragments together to form one continuous strand
37
What are exons?
They are the coding regions of DNA
38
What is the function of exons?
They exit the nucleus in the form of mRNA to be coded into proteins at the ribosome
39
What are introns?
They are the non-coding regions of DNA
40
What are introns?
They are the non-coding regions of DNA
41
What is the function of introns?
They stay inside the nucleus as they don’t need to be coded into proteins at the ribosome
42
What is a codon?
A set of three bases
43
What does each codon code for?
One amino acid OR STOP/START code
44
What is degeneracy of the genetic code?
This means that amino acids can be coded by more than one codon
45
Which two amino acids are not degenerate?
Methionine Tryptophan
46
What term is used to refer to codons which refer to the same amino acid?
Synonyms
47
Where do variations between synonyms occur? What is this called?
Third base of the codon Wobble position
48
Why is degeneracy of the genetic code important?
This minimises the effect of genetic mutations, as alterations to the base sequences are less likely to alter the protein being coded for
49
What amino acid is termed as the START codon?
Methionine
50
What is the function of the START codon?
This this is the signal for protein synthesis to begin
51
Why do not all polypeptides begin with methionine?
It can be removed at a later stage
52
What are the three types of RNA?
mRNA (messenger RNA) tRNA (transfer RNA) rRNA (ribosomal RNA)
53
What is the function of mRNA?
It is involved in transporting the genetic code from the nucleus to the ribosome so that protein synthesis can occur
54
What is mRNA transcribed from?
DNA
55
What is the function of tRNA?
It is involved in linking codons to their specific amino acid at the ribosome
56
What does tRNA consist of?
Anticodons
57
What is the function of anticodons?
They are able to pair to the codons on the mRNA chain When this pairing occurs, the amino acid held by the tRNA molecule is joined onto the growing chain of amino acids
58
What is rRNA?
A component of ribosomes
59
Where is rRNA produced?
Nucleus
60
Where is rRNA transported to?
Cytoplasm
61
What does rRNA combine with to form a ribosome?
Proteins
62
What is alternative splicing?
It is a process by which the exons of the RNA are reconnected in multiple ways during RNA splicing The resulting different mRNAs may be translated into different protein isoforms; thus, a single gene may code for multiple proteins
63
What is the number of chromosomes, autosome pairs and sex chromosome pars in a normal human cell?
Chromosomes - 46 Autosome pairs - 22 Sex chromosome pairs - 1

Year Three - Specialities (15 decks)

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