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Biology U3 &U4 > U4T1 - DNA | Tom > Flashcards

U4T1 - DNA | Tom Flashcards

Learn it probably idk just give it a red hot go mate and pray that you will learn it in time for the exam. Also good luck this is the hardest topic. Furthermore, I would personally wish you good luck to do well on the biology external. This deck was produced by Tom Hills and I henceforth declare all copyright laws so do not copy it or I will sue you for millions of dollars. I have no eyed deer how many words it will allow the description to be so I'm just gonna stop now.

1
Q

What is the repeating structure that make up DNA?

A

Nucleotides

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2
Q

What makes up a nucleotide?

A
  • A phosphate group
  • A sugar
  • A nitrogen-containing base
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3
Q

What are the 5 nitrogenous bases?

A
  • Adenine (A)
  • Guanine (G)
  • Cytosine (C)
  • Thymine (T) - Only in DNA
  • Uracil (U) - Only in RNA
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4
Q

What are the complementary base pairs?

A

A pairs with T
G pairs with C
U replaces T in RNA

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5
Q

What shape does DNA take and how are the strands described?

A
  • Double helix
  • The two strands are described as anti-parallel, they run in opposite directions.
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6
Q

What protein does DNA wrap around to form nucleosomes

A

Histone proteins

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7
Q

Where is DNA found in a Eukaryote?

A

Nucleus and some is found in mitochondria and chloroplasts as unbound circular DNA

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8
Q

Where is DNA found in Prokaryotes?

A

Cytoplasm as unbound circular DNA

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9
Q

What is chromatin?

A

Multiple nucleosomes packed together to form a fiber of chromatin.

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10
Q

What is a chromosome

A

tightly coiled and condensed form of DNA which is only visible during cell division.

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11
Q

What is the enzyme that ‘unzips’ DNA?

A

Helicase

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12
Q

What enzyme creates the complementary strand of DNA in the process of DNA replication?

A

DNA polymerase

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13
Q

What direction does DNA polymerase move along the strand during DNA replication?

A

5’ end to 3’ end

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14
Q

What is meiosis used for?

A

Production of gametes (sex cells: sperm and egg)

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15
Q

What is the difference between haploid and diploid?

A

Haploid cells contain half the number of chromosomes than diploid (23 chromosomes in humans)
- Gametes are haploid

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16
Q

What are somatic cells?

A

Diploid cells in the body (Any cell except gametes)

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17
Q

What are homologous chromosomes?

A

Two different chromosomes (one from mother, one from father) that encode for the same information

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18
Q

What is crossing over and recombination during Meiosis 1?

A

When non sister chromosomes within a homologous pair overlap and share genetic information (Where the overlapping occurs is random and can occur up to 25 times for each pair)

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19
Q

What are germ cells?

A

They give rise to gametes through Meiosis 1 and 2

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20
Q

How many sperm cells are created for every one germ cell?

A

4 haploid sperm cells

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21
Q

How many viable gametes does oogenesis produce?

A

1 haploid gamete (ova) for every 1 germ cell. There are three other haploid cells produced however they are no viable.

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22
Q

When does each stage of oogenesis occur?

A

Mitosis: before birth
Meiosis I: at puberty
Meiosis II: at pregnancy

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23
Q

What are the similarities and differences between spermatogenesis and oogenesis?

A

Similarities:
- Both processes form haploid cells from an original diploid cell
- Precursor cells undergo mitosis before meiosis occurs
- Hormones regulate and control both processes

Differences:
- Spermatogenesis produces 4 haploid spermatozoa. Oogenesis produces only 1 haploid ovum and 3 smaller, inviable polar bodies
- Precursor cell in spermatogenesis is spermatocyte. In oogenesis precursor cell is called oocyte.
- (In humans) Spermatogenesis is a continuous process beginning at puberty whereas oogenesis is a discontinuous process.

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24
Q

What is independent assortment?

A

Homologous chromosomes take a random position on either side of the equator of the germ cell during metaphase 1 to increase genetic variation

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25
What is random fertilisation?
When two people reproduce the random chance of any one sperm and egg coming together is estimated to have 70 trillion combinations. This also contributes to genetic variation.
26
What is a gene?
A sequence of nucleotides that encodes the synthesis of RNA or protein
27
What is a genome?
The complete set of genetic material present in an organism. Is measured in the number of base pairs contained.
28
What is a codon?
Three bases that code for an amino acid.
29
What is transcription?
The process in which DNA is copied into messenger RNA (mRNA)
30
What are the coding regions of DNA called?
Exons
31
What are non-coding regions of DNA called?
Introns
32
What is the purpose of non-coding DNA?
Telomeres contain short repeating sequences of DNA that protect chromosomes from damage. Centromeres contain non-coding DNA to assist in chromosome separation. There are many functions yet to be discovered.
33
What are the common features of eukaryotic genes?
- Start and stop codons - Promoter regions - Exons - Introns
34
Translate this sequence of bases into mRNA: AGCTACCGTAG
UCGAUGGCAUC
35
How is mRNA produced?
The two strands of DNA are separated and an mRNA strand is produced from the template strand of DNA. bases are added to the mRNA using complementary base pairing and the enzyme RNA polymerase
36
Where does transcription occur?
Inside the nucleus
37
What is the initiation phase of transcription?
RNA polymerase bind to the promoter region of the gene (TATA) and breaks strands to separate DNA and creates a transcription bubble. Transcription factors bind near promoter region to assist in initiation
38
What is the elongation phase of transcription?
RNA polymerase moves along gene, nucleotides added through complementary base pairing DNA reforms double helix behind transcription bubble mRNA is synthesised in 5' to 3' direction
39
What is the termination phase of transcription?
Transcription ends when RNA polymerase reaches a stop codon. This causes it to detach as well as the mRNA which undergoes processing to prep for translation
40
What happens in the processing stage after transcription?
- A cap is added to the 5' side of the mRNA and a poly-A tail is added to the 3' end. It consists of up to 250 adenine nucleotides to increase stability of mRNA - Intron splicing: non-coding regions are cut from mRNA by spliceosome.
41
What does RNA translation achieve?
It uses info from mRNA to build an amino acid chain (polypeptide chain) Note: translation occurs in cytoplasm
42
What do codons code for?
A codon is made of 3 bases which correlates to a specific amino acid Eg: AUG - start codon UAA - stop codon (there are 2 others)
43
What is a ribosome and what does it do?
It consists of 2 subunits that come together around the mRNA and produces a peptide chain based on the codons on the mRNA
44
What is tRNA and what does it do?
Transfer RNA its adds specific amino acids to the chain based on the codon on the mRNA. For every codon, the tRNA brings the corresponding amino acid using its anticodon
45
What is an anticodon?
A sequence of 3 nucleotides on tRNA which is complementary to the codon on the mRNA
46
Name the three phases of transcription and translation
Both processes have the phases of: - Initiation - Elongation - Termination
47
What is initiation in the process of translation?
Ribosome assembles around 5' end of mRNA and first tRNA is put in place at the AUG codon on the mRNA This is called the initiation complex
48
What is elongation in the process of translation?
mRNA is shifted through the ribosome and tRNA brings in complementary anticodons with corresponding amino acids which join the chain
49
What is termination in the process of translation?
Attachment continues until stop codon is reached which releases the polypeptide chain which gets folded and processed within the cell.
50
What is the purpose of gene expression?
To produce a functional gene product (It can be regulated)
51
What factors can regulate gene expression?
- Transcription (transcription factors) - Products of other genes (some genes produce proteins or signaling molecules that can activate other genes) - Environmental exposure (consider the twin studies in lesson 7 pp)
52
What are transcription factors?
Proteins that can bind to DNA or DNA polymerase to promote or suppress specific genes.
53
What is cell differentiation controlled by
Transcription factors that can control cell morphology or tissue formation (determines what the cell becomes eg, heart cells, nerve tissue ect.)
54
Give an example of a transcription factor gene that regulates morphology
- SRY gene, the Y chromosome in males codes for a transcription factor protein that turns on male genes which form the male sex organs when expressed. - Hox genes: Harder than SRY and you only need to know 1 example to just do SRY cus its easier
55
What are the possible causes of a mutation?
Can result from errors in: - DNA replication - Cell division or cause from damage by mutagens
56
What are point mutations?
A singular base is changed in the DNA sequence.
57
What are frameshift mutations?
Involves the insertion or deletion of one or more bases, shifting several codons.
58
What is nondisjunction?
During cell division, chromosomes can fail to separate correctly and can result in aneuploidy.
59
What is a karyotype?
Full set of chromosomes in a person
60
What is aneuploidy and give an example.
An abnormal number of chromosomes. Example: Trisomy 21, results from an extra chromosome in pair 21.
61
What are the three categories of mutagens?
Physical: ionising - Alpha rays, beta rays. Non ionising - UV ratiation Chemical: pesticides, alkylating agents Biological: Bacteria/virus
62
How do mutagens affect DNA?
They can cause breaks in DNA, replace bases, create abnormal bonds between bases, activation of growth genes, and causes rate of mutation to increase.
63
What are the three types of inheritance patterns?
- Autosomal dominant - Sex-linked - Multiple allele
64
What is DNA sequencing and what is it used for?
determining the entire DNA sequence of an organism. Scientists can determine specific genes and can identify unique sections that may cause disease. DNA sequencing can also be used to map species and determine how different one species is form another based on differences in sequencing
65
What is an autosomal dominant trait?
- The trait is the result of a dominant allele on an autosome - Gene must be on chromosome pair 1 to 22 - A.K.A. 'complete dominance'
66
What is the purpose of polymerase chain reactions (PCR)?
Lab technique that is designed to replicate stands of DNA often used for forensics.
67
- Father's genotype is Bb (affected) - Mother's genotype is bb (unaffected) Which genotypes will present as affected?
- BB (not in this case) - Bb Only one dominant allele is required to show trait.
68
What is gel electrophoresis?
Used to sperate DNA, RNA or proteins according to molecular size. Can be used to compare DNA fragments. Can be used for paternity testing.
69
What is a sex-linked trait?
- Requires gene to be on chromosome pair 23 - Much more common on X chromosome (X-linked) - Different inheritance pattern for males & females
70
Father: XD Y (unaffected) Mother: Xd Xd (affected) What are the chances for a son and a daughter to be affected?
- Son: 100% chance to be affected - Daughter: 0% chance to be affected, 100% chance to be a carrier
71
What is incomplete dominance?
- Neither allele is completely dominant - Blended phenotypes - E.g. Red + White = Pink
72
What is DNA sequencing and how is it used?
The process of determining the DNA sequence of an organism. Can be used to identify genes that code for specific phenotypes (Genetic disease, possible treatment targets). Can also be used to compare sequences of different organisms to determine evolutionary relationships and classification.
73
What is the purpose of the Polymerase chain reaction process (PCR)?
Used to amplify DNA sequences allowing a single or a few copies of DNA to be replicated into millions of copies. Allows DNA to be studied in detail.
74
What is the purpose of gel electrophoresis?
Used to separate DNA, RNA or proteins according to molecular size. Can be used to compared DNA fragments for: - DNA screening and profiling. - Confirming the correct gene has been amplified in PCR. - Identifying DNA fragments obtained by restriction enzyme digestion.
75
What is recombinant DNA and what is it created for?
When DNA from two different sources are joined together. Typically a DNA fragment and a Vector (oh yeah!) They are created to clone a particular gene and/or produce large quantities of the protein expressed by the cloned gene. (Example would be an insulin-coding gene being incorporated into a bacteria to produce insulin for diabetes)
76
What is involved in Step 1 of recombinant DNA (Isolation and cutting of DNA)?
Restriction enzymes are used to find specific recognition sequences called restrictions sites. These enzymes then cut the DNA into smaller more usable fragments.
77
What is involved in Step 2 of recombinant DNA (Insertion of DNA into plasmids)? Also explain what a plasmid is.
Recombinant DNA is placed into plasmids which are its vector (oh yeah!) allowing it to replicate within the bacteria. Plasmids are small circular pieces of (double stranded) DNA which replicates independently of the chromosomes present in the bacteria.
78
What is involved in Step 3 of recombinant DNA (Joining of DNA)?
Groups of enzymes called ligases, join fragments of the spliced DNA with plasmids in a process called ligation. Allows the enzymes to join segments of newly replicated DNA and repair strands.
79
What is involved in Step 4 of recombinant DNA (Amplification of recombinant DNA)?
Recombinant DNA is mixed with bacteria that is heat shocked to take up a recombinant plasmid in a process called transformation. Additionally, the bacteria is selected and grown to form a colony by including antibiotic resistant DNA within the plasmid. The colony is grown in bulk to amplify the gene and make protein

Biology U3 &U4 (4 decks)

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