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Biology Unit 2 > Genetics > Flashcards

Genetics Flashcards

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1
Q

What elements are there in Nucleotides?

A

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphate (CHONP)

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2
Q

What is the composition of a Nucleotide?

A
  • A negatively charged phosphate group which makes it acidic
  • A pentose sugar called deoxyribose
  • A nitrogenous base.
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3
Q

What are the four types of nitrogenous bases/nucleotides?

A
  • (A) Adenine makes Adenosine
  • (C) Cytosine makes Cytidine
  • (G) Guanine makes Guanosine
  • (T) Thymine makes Thymidine
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4
Q

What is the variability in the number of phosphate groups a nucleotide can have?

A

A nucleotide can have 1, 2 or 3 phosphate groups.

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5
Q

Explain Nucleotide Polymerisation.

A

Nucleotides form phosphodiester bonds in a condensation reaction between Carbon 3 of the sugar and an oxygen atom in the phosphate, creating a sugar-phosphate backbone, so the bases can connect with other bases in other nucleotides. The new polymer has a free phosphate group at the 5’ end and a free OH group at the 3’ end

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6
Q

What are the main features of DNA?

A
  • Double stranded; two antiparellel nucleotides alongside each other.
  • Double Helix
  • Bound together by hydrogen bonds between bases forming base pairs.
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7
Q

What is DNA made of?

A

Nucleotides

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8
Q

What are complementary base pairs?

A

The only pairing of bases that will bond together. A and T, C and G, etc.

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9
Q

How does the structure of DNA make it well suited for storing and expressing genetic information?

A
  • The bases are protected on the inside of the molecule, and the molecule is very stable as it is held together by many hydrogen bonds
  • DNA is long and tightly coiled so it can store a lot of information.
  • Two complementary strands means two copies of information, which is useful for repair, copying and error checking.
  • Bases act as a 4 letter alphabet.
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10
Q

Where does DNA replication start?

A

A specific sequence on the DNA molecule called the replication origin.

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11
Q

What enzyme unwinds and separates the two strands of DNA in the process of DNA replication?

A

DNA Helicase

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12
Q

What is the new DNA in DNA Replication built up from?

A

Free nucleotides that are present in the nucleoplasm that bind to the old strands by complementary base pairing

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13
Q

What enzyme joins the nucleotides that have paired to an old strand together during DNA replication?

A

DNA Polymerase

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14
Q

What kind of bond are nucleotides bound together by in DNA?

A

Phosphodiester bonds, forming the sugar phosphate backbone.

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15
Q

Once DNA Polymerase has formed newly paired nucleotides into another strand, what occurs?

A

Another enzyme winds the old strands with the newly made strands to make two double Helices, which are copies of the original DNA

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16
Q

How was the mechanism of semi-conservative replication proven?(each new strand having one old and one new strand)

A

Density gradient centrifugation.

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17
Q

What are the functions of DNA?

A

To make proteins of a specific shape and function

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18
Q

What two definitions are there for a gene?

A
  • A gene is an inherited factor that controls a particular characteristic
  • . . . A section of DNA that codes for a particular polypeptide
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19
Q

What is the process of genes controlling characteristics called?

A

Gene expression

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20
Q

How many bases are in a codon?

A

3 bases

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21
Q

How many different combinations of bases can there be in a codon?

A

64

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22
Q

How is the sequence of bases important in determining the characteristics of a cell?

A

The sequence of bases determines the sequence of amino acids which determines the shape and function of the protein (which determines the characteristics of the cell)

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23
Q

What are the two types of non coding DNA?

A

Introns and Satellite DNA?

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24
Q

What is another name for coding DNA?

A

Exons

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25
What are introns?
Non coding DNA within a gene
26
What is satellite DNA?
Non coding DNA in between genes
27
What makes non coding DNA useful if it does not determine characteristics/code for specific proteins?
- Assists in coiling DNA into chromosomes - Has a control function, regulating when genes are to be expressed - Involved in DNA replication - contains unused copies of genes (pseudo genes)
28
What is the sum of all of the genes in an organism called?
A genome
29
What is a mutation in terms of DNA?
A base pairing error that occurs during DNA replication that causes a change in the characteristic of the cell the protein is coded for.
30
How does a mutation cause a change in a characteristic of a cell?
A base pairing error causes a change in the sequence of amino acids in the polypeptide which changes the primary, secondary and tertiary structure of the protein, changing its function, which causes a change in the function of the cell overall.
31
What is an allele?
A different version of a gene
32
What is a genotype?
A set of genes in our DNA that is responsible for a certain trait or characteristic
33
What is a phenotype?
The physical expression of the trait the genotype is responsible for
34
What are silent mutations?
Mutations that result in no phenotypic effect. They do not change the protein or are not expressed in the cell
35
Given that a DNA molecule is 1m long, how can it fit into the nucleus of a cell?
It is cut into shorter lengths and tightly wrapped around histone proteins to form chromatin which replicates and forms chromosomes
36
Why are chromosomes roughly X shaped?
Because they contain two replicated copies of DNA.
37
What is one copy of DNA in a chromosome during DNA replication called?
A chromatid
38
What is the name of the location where two chromatids are joined to form a chromosome?
Centromere
39
How is prokaryotic DNA different to eukaryotic DNA?
- It is much shorter - It is a closed loop - It is not associated with histone proteins
40
What is a Karyotype?
A Karyotype is the number and appearance of chromosomes in the nucleus of a eukaryotic cell.
41
What are homologous pairs of chromosomes?
Chromosomes that have the same size shape and banding pattern
42
How many pairs of chromosomes do humans have?
23
43
Are male sex chromosomes homologous or non homologous?
Non homologous
44
What are non sex chromosomes called?
Autosomal
45
Why do we have two copies of each chromosome?
We inherit one copy from each parent
46
What does an ideogram represent?
The long coiled DNA molecule in one chromosome
47
What does it mean for a gene to be homozygous in terms of chromosomes?
Both the paternal and maternal chromosomes have the same allele
48
What does it mean to be heterozygous in terms of chromosomes?
The maternal and paternal versions have different alleles of the gene
49
Genes are distributed along the DNA that comprises a chromosome. What is the defined position of a gene called?
The locus
50
How are new cells formed in the body?
Mitosis
51
What are the four purposes of making new cells through mitosis?
- Growth - Replacement - Repair - Reproduction(Asexual)
52
What are the two main phases of the cell cycle in mitosis?
Interphase and the Mitotic Phase
53
Explain Interphase
Where the cell grows and does whatever it is meant to do. Can be split into Growth Phase 1 , Synthesis Phase and Growth Phase 2
54
What is Growth phase 1 of interphase?
Where cells grow to their original size, genes are expressed and organelles are replicated
55
What is synthesis phase of Interphase?
Where DNA and histones are replicated in perpetration for mitosis
56
What is the second growth phase in Interphase?
Where spindle proteins are synthesised, ready for mitosis
57
What are the four sub stages of the Mitotic stage?
- Prophase - Metaphase - anaphase - telophase
58
Explain the details of Prophase in mitosis
- Chromosomes condense and are visible - Centrioles at opposite poles of the cell - Nucleolus disappears
59
Explain metaphase in mitosis
- Nuclear envelope disappears - chromosomes align along equator of cell - Spindle fibres connect the centrioles to the chromosomes
60
Explain anaphase in mitosis
- Centromeres split allowing chromatids to split | - Chromatids move centromere-first to the centrioles, pulled by motor proteins walking along the micro tubule tracks
61
Explain Telophase
- Spindle fibres disperse - nuclear envelopes form around both groups of chromatids - chromatids uncoil and become too thin to see
62
Explain cytokinesis in mitosis
- A ring of actin filaments forms around the equator of the cell and tightens to form a cleavage furrow which splits the cell (Animals) - Vesicles move towards the equator and line up to fuse into two membranes called the cell plate, which a new cell wall is laid down in between (Plants)
63
What occurs after mitosis in a multicellular organism?
Cell differentiation; turning on all of the required genes and turning off all the others
64
What is Meiosis?
Special cell division in sexually reproducing organisms to make gametes.
65
What is the difference between mitosis and meiosis?
There are two divisions instead of one, which results in 4 haploid cells (half number of chromosomes) instead of 2 diploid cells
66
What is the particular way in which the chromosome number is halved in meiosis?
Each haploid cell has one of each homologous pair of chromosomes.
67
What is genetic recombination and where is it used?
Where chromosomes rearrange to form new combinations of alleles found in meiosis
68
Why is genetic recombination significant for meiosis?
It is a major source of genetic variation
69
What are the three types of genetic variation?
- Independent assortment - Crossing over - Random fertilisation
70
Explain independent assortment and when it happens during the process of meiosis
During the first meiosis division, the homologous chromosomes join together to form 'bivalents' that line up on the equator, but each bivalent is made up of two maternal and paternal chromosomes that can line up in any order which means the chromosomes will be mixed up in the final gametes
71
Explain 'crossing over' in meiosis and how it leads to genetic variation
When the bivalent said are formed, bits of one chromosomes are crossed over with the corresponding bits of other chromosome, creating chiasmata, which allows paternal and maternal chromosomes to combine
72
What is a chiasmata?
The point at which chromosomes cross over during the forming of bivalent a in the first meiotic division, which involve large multi enzyme complexes to cut and join the DNA. (Can be seen under microscope because it changes the shapes of the chromosomes)
73
What is Random Fertilisation?
When two gametes fuse to form a zygote.
74
What is the key aspect of a therapeutically useful antimicrobial agent(antibiotic)?
Must be selectively toxic; only targets microbes growing in human tissue and not the human host cells themselves.
75
How can antibiotics be selectively toxic?
They inhibit enzymes that are unique to prokaryotic cells, like ribosomes.
76
How does penicillin work?
It inhibits an enzyme which is involved in the synthesis of peptidoglycan for bacterial cell walls, killing bacterial cells by osmotic lysis as the cell wall bursts from the higher water potential outside the cell.
77
How do bacteria become resistant to antibiotics?
Mutations may occur which change the shape of an active site to bind the antibiotic (like penicillin with penicillinase) or it could alter a ribosome so that streptomycin inhibitors can no longer bind.
78
How does vertical gene transmission lead to antibiotic resistance in bacteria?
When a bacteria develops a mutation which makes them resistance to an antibiotic, they asexually reproduce by binary fission, and pass on the resistance to its offspring
79
Explain horizontal gene transmission
The transfer of genes between bacteria through conjugation
80
How does bacterial conjugation work?
When bacteria join together and transfer DNA in the form of one or more plasmids via cytoplasmic bridges/piluses.
81
What is bacterial multiple resistance?
When a resistant strain of bacteria develops resistance to more than one antibiotic due to horizontal gene transmission

Biology Unit 2 (4 decks)

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