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Genetics Flashcards

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1
Q

What is the genetic code?

A

The order of triplet bases with each coding for a particular amino acid (codon)

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2
Q

What is the human genome

A

The complete DNA sequence of a human including mitochondrial DNA

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3
Q

What is a Diploid

A

A cell that has two copies of each chromosome

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4
Q

What is a Haploid

A

A cell that only has half the number of chromosome

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5
Q

What is chromatin

A

A highly condensed structure made of DNA and RNA that forms chromosomes

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6
Q

What is a Histone

A

Any group of basic proteins found in chromatin

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7
Q

What is a chromosome

A

A threadlike structure of nucleic acids and protein found in the nucleus of most cells, it carries genetic information

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8
Q

What is a gene

A

A unit of heredity which is transferred from a parent to an offspring

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9
Q

What is DNA Helicase

A

It breaks the hydrogen bonds between bases and unwinds the double helix

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10
Q

What is DNA Polymerase

A

Catalyses phosphodiester bonds between the nucleotides when rebuilding the second strand of DNA

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11
Q

What is DNA Ligase

A

Joins together fragments of newly synthesised DNA to make a seamless strand

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12
Q

What does non-overlapping mean?

A

Each triplet is only read once and triplets don’t share any bases

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13
Q

What does degenerate mean?

A

More than one triplet codes for the same amino acid- reduces the number of mutations

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14
Q

How does DNA differ in eukaryotic and prokaryotic cells

A

In eukaryotic it in long and linear and associated with proteins (histones)

In prokaryotic it is short, circular and not associated with proteins

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15
Q

What is the structure of mRNA?

A

A long single strand created during transcription that has a base sequence complementary to DNA,

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16
Q

What is the structure of tRNA?

A

Small molecules made of around 80 nucleotides,

It is a small strand folded into a clover leaf shape,

One end and amino acid attaches and at the opposite end is an anti-codon that is specific to the amino acid

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17
Q

What happens in transcription?

A

DNA Helicase breaks the hydrogen bonds between the DNA strands,

Free nucleotides slot into the antisense strand,

RNA Polymerase joins the bases by phosphodiester bonds- forming a molecules of mRNA,

The pre-mRNA is then spliced to remove the introns- leaving a strand of exons,

The mRNA then moves out of the nucleus through a nuclear pore,

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18
Q

How does translation work?

A

mRNA attaches to a ribosome and tRNA collects amino acids from the cytoplasm and carried them to the ribosome,

tRNA attaches itself to mRNA by complementary base pairing,

The amino acids attached to two tRNA molecules joined by a peptide bond and then tRNA molecules detach themselves from the amino acids

The process is repeated leading to a polypeptide chain until a stop codon is reached on mRNA and ends the protein synthesis,

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19
Q

What is a substitution mutation?

A

When one nucleotide in the DNA sequence is replaced by another- changes a single amino acid- but the substituted nucleotide may code for the same amino acid

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20
Q

What is a deletion mutation?

A

When a nucleotide in the DNA sequence is lost, Can lead to a frame shift, resulting in completely different amino acids being coded for

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21
Q

What is a polyploidy mutation?

A

When an individual has three or more sets of chromosomes instead of two- common in plants

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22
Q

What is a non-disjunction mutation?

A

When chromosomes fail to separate correctly in meiosis- the gametes an zygotes formed will have one more or one less chromosomes than they should- down’s syndrome is a result of non-disjunction

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23
Q

What is Meiosis?

A

Cell division that produces 4 daughter cells that are all genetically different and have half the number of chromosomes as in the parent cell

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24
Q

What is the point of meiosis?

Study These Flashcards
A

To produce genetically different cells and genetic variation

25
How is genetic variation achieved through independent assortment of chromosomes?
There are various combinations of chromosome arrangement, homologous chromosomes line up in pairs, the arrangement of the pairs is random so the division into the daughter cells is also random
26
How is genetic variation achieved through the crossing over of chromatids?
When pairs of chromosomes line up they can exchange some of their genetic material
27
What happens during Meiosis 1?
Homologous chromosomes pair up whereby crossing over at the chiasmata may take place, the cell then divides whereby each daughter cell contains one chromosome from each homologous pair
28
What happens during Meiosis 2?
The chromatids of each chromosome are separated producing 4 haploid daughter cells
29
How do alleles affect genetic diversity?
If there are more alleles in a species then there is a larger gene pool so more genetic diversity
30
What is an allele?
When there are multiple versions of the same gene
31
How does genetic diversity increase in a population?
Mutations- creations of new alleles Gene flow- introduction of new alleles by migration
32
What is a genetic bottleneck
When a major event wipes out a lot of an organism, leaving a small population of survivors and decreasing the gene pool so when the survivors breed they are more vulnerable to disease as the gene pool is smaller
33
What does genetic variation allow?
Natural selection
34
What is natural selection
Individuals with a fitter phenotype are more likely to survive and pass on their alleles to their offspring
35
What does natural selection do
It increases the frequency of advantageous alleles and decreases the frequency of harmful alleles
36
What is the founder effect
When a small number of organisms from a large population colonise a new region
37
What can cause the founder effect
Geological events such as volcanic eruptions
38
What happens to the new colony after they move
They have a much smaller gene pool than the original population, so much lower genetic diversity
39
What is an advantageous allele
The organism is more likely to survive and reproduce successfully, the allele will be passed to the offspring who are more likely to survive and so pass onto more offspring- increasing the allele frequency
40
What is allele frequency
How often a particular allele appears in a population
41
What is stabilising selection
A type of selection that favours individuals with phenotypes that are closer to the mean and not extremes
42
What is disruptive selection
Natural selection where extreme values of a trait are valued over intermediate ones
43
What is directional selection
Natural selection where a single phenotype is favoured, causing allele frequency to continuously shift in one direction
44
What does HIV being a retrovirus mean
It can make DNA from RNA
45
What is on the viral envelope that is an advantage to HIV
- A lipid bilayer which increases infectivity - Viral glycoproteins that enable the virus to dock on to host glycoproteins - Host cell glycoproteins have been stolen and incorporated into the HIV membrane, increasing infectivity
46
How does HIV enter the host cell
1. HIV will be circulating in the bloodstream, the gp120 attachment protein will bind to the CD4 receptor on the surface of a host cell, The viral envelope fuses with the cell membrane of the host cell, allowing viral entry to the cell
47
How is viral DNA produced
The reverse transcriptase enzyme will move along the viral RNA strand, this leads to the production of a ds viral DNA molecule
48
How is viral DNA integrated into the host cells DNA
During integration, the double-stranded portion of viral DNA will travel into the nucleus and will be integrated into the host cells DNA by and enzyme called integrase
49
What does genomic RNA do
It serves as a messenger RNA< containing the instructions needed to synthesise viral proteins and RNA needed to make new HIV particles
50
How are new HIV particles made
Newly synthesised viral proteins and viral RNA are used to assemble new HIV particles
51
What is the final stage in HIV replication and infection
The newly assembled HIV particle will break away (budding off) from the host cell, with a piece of its cell surface membrane surrounding it which forms the lipid envelope
52
How does HIV cause AIDs?
HIV kills or interferes with the normal functioning of T Helper cells, as a result the body is unable to produce an adequate immune response, and the person becomes highly susceptible to other infections and cancer, they can develop infections and illness
53
Why do you have to use aseptic technique when handling bacteria
To prevent contamination of the specific microorganism you are working with, and also to try and reduce your chance of being exposed to it
54
What is a broth
A nutrient dense liquid that provides the perfect conditions for bacteria to thrive and multiply
55
Why do you not completely seal the petri dish during incubation
The bacteria needs oxygen to survive
56
Why do you spread the antibacterial disks apart on the agar plate
So they don't interfere with each others results
57
Why must the wire loop be cooled after flaming
If it is too hot it may kill the bacteria when you pick them up
58
Why is the neck of the vessel containing the broth warmed
To prevent contaminants from entering the bottle
59
Why do you work near a Bunsen burner
It provides an up flow of air which carries potential contaminants away from the agar plate and broth

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