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Biology > Grade 12 - DNA & RNA - Life at the molecular, cellular and tissue level > Flashcards

Grade 12 - DNA & RNA - Life at the molecular, cellular and tissue level Flashcards

1
Q

What does DNA stand for?

A

DEOXYRIBONUCLEIC ACID

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2
Q

What is DNA?

A

Nucleic acid that composes chromosomes and carries genetic information.

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3
Q

CHROMOSOME ORGANIZATION

A
  1. A chromosome is an enormous strand of super coiled DNA.
  2. Sections of DNA on the chromosome that code for proteins are called genes.
  3. Noncoding sections of DNA used to be called “junk DNA” (regulatory or unknown function)
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4
Q

Explain the relationship between Chromosomes and Genes

A
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5
Q

Explain the building blocks of DNA

A

Composed of nucleotides

Nucleotides contain three parts:

  1. 5-Carbon Sugar (deoxyribose)
  2. Phosphate Group
  3. Nitrogen Base
    (four types: adenine, guanine,
    thymine and cytosine)
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6
Q

What are Adenine and Guanine?

A

Adenine and Guanine are purines (composed of two rings of nitrogen atoms)

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7
Q

What are Thymine and Cytosine?

A

Thymine and Cytosine are pyrimidines (composed of one ring of nitrogen atoms)

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8
Q

Explain the structure of DNA:

A

Consists of two strands of nucleotides that form a twisted ladder (double helix)
Sugar and phosphate alternate along the sides of the ladder (linked by strong covalent bonds)
Pairs of nitrogen bases form the rungs of the ladder (linked by weak hydrogen bonds).

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9
Q

Explain Chargaff’s Rule:

A

Specific base pairing arrangement
A-T : 2 hydrogen bonds
C-G : 3 hydrogen bonds

Nitrogen bases attach to the sugar portion of the side (NOT the phosphate)

Strands run in opposite directions

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10
Q

What is the function of DNA?

A

DNA codes for proteins (structural proteins, enzymes, and hormones)

information for building proteins is carried in the sequence of nitrogen bases

proteins determine physical and metabolic traits and regulate growth and development.

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11
Q

DNA REPLICATION

A

Definition: the process of making a new DNA molecule from an existing DNA molecule that is identical to the original.

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12
Q

Where does DNA Replication take place?

A

The nucleus of the cell – during interphase of mitosis (in between cell divisions)

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13
Q

What is the purpose of DNA Replication?

A

DNA replication ensures that the genetic code is transferred to each daughter cell.

This gives daughter cells produced by cell division a complete set of genetic information identical to the parent cell.

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14
Q

During which phase does replication occur?

A

Interphase (s)

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15
Q

PROCESS OF REPLICATION(Description of diagram)

A
  • Helicase enzymes unzip the parent strand by separating the nitrogen base pairs.
  • DNA polymerase pairs free DNA nucleotides in the nucleoplasm with the exposed bases on both strands following the base pair rules.
  • Hydrogen bonds reform spontaneously sealing the two strands of each DNA molecule together.
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16
Q

What are the results of replication?

A
  1. Two molecules of DNA that are identical to the original DNA strand.
  2. Each is half old (strand from parent) and half new (strand synthesized by DNA polymerase)
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17
Q

What does RNA stand for?

A

Ribonucleic Acid

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18
Q

What is RNA?

A

Nucleic acid involved in the synthesis of proteins

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19
Q

What is RNA STRUCTURE composed of?

A
  • RNA is composed of nucleotides, but these differ from DNA in three ways.
  • Single strand of nucleotides instead of double stranded.
  • Has uracil instead of thymine.
  • Contains ribose instead of deoxyribose.
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20
Q

What is the function of RNA?

A

Three forms of RNA involved in protein synthesis
What is protein
1. mRNA (messenger): copies instructions in DNA and carries these to the ribosome.
2. tRNA (transfer): carries amino acids to the ribosome.
3. rRNA (ribosomal): composes the ribosome.

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21
Q

What is protein synthesis?

A
  • Cells build proteins following instructions coded in genes (DNA).
  • Consists of two parts, transcription and translation
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22
Q

TRANSCRIPTION

A

**DNA is copied into a complementary strand of mRNA.

WHY?
* DNA cannot leave the nucleus. Proteins are made in the cytoplasm. mRNA serves as a “messenger” and carries the protein building instructions to the ribosomes in the cytoplasm.

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23
Q

LOCATION OF TRANSCRIPTION

A

Nucleus

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24
Q

HOW TRANSCRIPTION OCCURS

A
  1. RNA polymerase untwists and unzips a section of DNA (usually a single gene) from a chromosome.
  2. RNA polymerase pairs free RNA nucleotides to the exposed bases of one of the DNA strands following base pair rules.
    Uracil replaces thymine
    Only 1 strand of DNA serves as a template, the other “hangs out”
  3. Newly synthesized mRNA separates from template DNA and DNA zips back up.
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25
Q

RESULT OF TRANSCRIPTION

A

mRNA strand with instructions for building a protein that leaves the nucleus and goes to the cytoplasm.

26
Q

TRANSCRIPTION EXAMPLE

A

Transcribe the following DNA Sequence in mRNA

TAC CGG ATC CTA GGA TCA
AUG GCC UAG GAU CCU AGU

27
Q

PROTEINS

A
  • Structural and functional components of organisms.
  • Composed of amino acids
  • order of nucleotides in DNA determines order of amino acids in a protein
  • One gene codes for one protein
28
Q

GENETIC CODE

A

The “language” that translates the sequence of nitrogen bases in DNA (mRNA) into the amino acids of a protein.

Codon = three nucleotides on DNA or mRNA

One codon specifies one amino acid

Some codons are redundant (code for the same amino acid)
The genetic code is universal to all organisms

29
Q

IMPORTANT CODONS

A

AUG = start translation (Met)
UAA, UAG, UGA= stop translation

30
Q

TRANSLATION

A

Instructions in mRNA are used to build a protein

31
Q

LOCATION OF TRANSLATION

A

ribosome (in the cytoplasm)

32
Q

Explain the PROCESS OF TRANSLATION (7)

A
  1. mRNA binds to the ribosome.
  2. Ribosome searches for start codon (AUG)
  3. tRNA brings correct amino acid (methionine) to the ribosome.
    Each tRNA carries one type of amino acid.
    The anticodon (three nitrogen bases on tRNA) must complement codon for amino acid to be added to protein chain
  4. ribosome reads next codon
  5. tRNA’s continue lining up amino acids according to codons
  6. peptide bonds link amino acids together
  7. ribosome reaches STOP codon
    Amino acid chain is released
33
Q

RESULT OF TRANSLATION

34
Q

DNA is often referred to as the “molecule of life”.

Explain why this statement can be regarded as correct.
(2)

35
Q

Draw and label the basic structure of a DNA nucleotide in the space below. (4)

36
Q

In a section of a DNA molecule there are 16 nucleotides. There are three adenine nitrogen bases in the section of DNA. Calculate the number of guanine nitrogen bases present. Show all working. (3)

37
Q

Describe the process of protein synthesis.

A

Use 2019 Life Science Paper 1 work sheet.

38
Q

Name the two nucleic acids that occur in a cell.

39
Q

Are nucleic acids considered to be organic or inorganic molecules?

40
Q

What are the monomers (building blocks) of nucleic acids called?

41
Q

Name 3 parts of a monomer of nucleic acids called?

42
Q

Name the sugar molecules that occur in DNA.

43
Q

Name the sugar molecules that occur in RNA.

44
Q

Name the different nitrogenous bases that occur in DNA

45
Q

Name the different nitrogenous bases that occur in RNA

46
Q

Name the nitrogenous bases that are purine bases.

47
Q

Name the nitrogenous bases that are pyrimidine bases.

48
Q

What is the natural shape of DNA?

49
Q

What is the natural shape of RNA?

50
Q

What type of bond is found between the purine and pyrimidine bases of DNA?

51
Q

Which characteristic of the bonds between the purine and pyrimidine bases of DNA will ensure that replication of DNA, as well as the transcription of mRNA, will take place quickly and easily.

52
Q

What is your understanding of the term DNA replication?

53
Q

During what stage of the cell cycle does replication take place?

54
Q

Describe the process of replication as it takes place in the DNA molecule.

55
Q

Distinguish between two types of mutations i.e. chromosomes and gene mutations.

56
Q

Name two factors that may accelerate the occurrence of mutations.

57
Q

Name 4 ways in which gene mutations may occur.

58
Q

A frame shift mutation has a greater effect than a point mutation. Refer to the difference between these two types of mutations to support this statement.

59
Q

Explain fully how it is possible that neutral / silent mutations may be harmless..

60
Q

Define DNA fingerprint / DNA profile and explain how it works:

A

A person’s unique DNA fragments that have been separated using gel electrophoresis.

How does it work?
* Uses non-coding DNA
* STRs (short tandem repeats)
* The number of repeats varies per person
* 13 to 20 sites/ locations/ loci can be checked

61
Q

Discuss how DNA profiling is used in forensic investigations and paternity tests / 5 Uses for DNA fingerprints

A

1. Forensics:
Suspects must have a complete match with DNA from the crime scene for a conviction to occur
2. Diagnosing inherited disorders:
Gives doctors information about diseases that can affect a couple’s children
3. Identifying casualties:
If the army kept a database of all soldiers DNA fingerprints, they could identify soldiers who are unrecognisable.
4. Paternity tests:
50% of the DNA from the child will come from the father. This can prove/ establish who the father is.
5. Fight illegal trading:
The origins of certain items/ materials can be traced and prevent illegal trading

62
Q

Discuss the disadvantages of DNA technology:

A

As amazing as this technology is, there are some people who would use this to harm others.
1. Violation of privacy
DNA profile data could get leaked
If inheritable diseases are found, medical aids might not cover indivuals

2. Accuracy?
The quality of equipment determines the effectiveness of the DNA fingerprint.
Could lead to false accusations/ convictions

3. Manipulation:
Tampering with evidence can occur
False accusations/ convictions can occur

Biology (25 decks)

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