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Higher Human > Unit 1: Human cells: 1.2 Structure and Function of DNA > Flashcards

Unit 1: Human cells: 1.2 Structure and Function of DNA Flashcards

1
Q

What is DNA a molecule of?

A

DNA is the molecule of inheritance and stores genetic information in its sequence of bases

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2
Q

What does the sequence of bases on DNA determine in an organism?

A

The sequence determines the organisms genotype and the structure of its proteins

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3
Q

What does DNA consist of?

A

Units called nucleotides

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4
Q

What are nucleotides?

A

DNA consists of two strands composed of repeating units called nucleotides

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5
Q

What are nucleotides made of?

A

Each nucleotide consists of a molecule of DEOXYRIBOSE SUGAR joined to a PHOSPHATE group and an organic BASE

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6
Q

What forms the genetic code?

A

The base sequence

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7
Q

What holds each strand of DNA together?

A

A chemical BOND forms between the PHOSPHATE group of one nucleotide and the DEOXYRIBOSE SUGAR of another nucleotide

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8
Q

How are two strands of DNA joined together?

A

Two strands of nucleotides are joined together

by HYDROGEN BONDS forming between COMPLIMENTARY BASES

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9
Q

What is the use of weak hydrogen bonds between strands?

A

The strands can become easily separated (for replication)

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10
Q

What is the base pair rule?

A

Each base can only join with one other type of base: Adenine(A) always bonds with Thymine(T) and Guanine(G) always bonds with Cytosine(C)

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11
Q

What does the term anti parallel describe?

A

Anti parallel is used to describe the structure of the two DNA strands as they run in opposite directions to each other

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12
Q

What is at the 5’end of a DNA strand?

A

Phosphate

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13
Q

What is at the 3’end of a DNA strand?

A

Deoxyribose sugar

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14
Q

What are histones?

A

Bundles of protein that molecules of DNA become tightly coiled and packaged around

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15
Q

What are the uses of histones?

A

They help in the STORAGE of the long structures (DNA) and they unwind again when required to do so

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16
Q

Why is DNA a unique molecule?

A

DNA is a unique molecule as it is able to direct its OWN REPLICATION and produce an EXACT COPY of itself

17
Q

What is essential prior to cell division and why?

A

DNA REPLICATION is essential prior to cell division so that each daughter cell contains the EXACT SAME genetic information as the original parent cell

18
Q

For DNA replication to take place what must the nucleus contain? Name 5

A 
DNA(to act as a template)
Primers(short sequence of nucleotides)
A supply of the four types of DNA nucleotides (ATGC)
Enzymes(DNA polymerase and ligase)
ATP
19
Q

Describe the first stage of the process of DNA replication

A

A starting point on the DNA molecule is recognised and the DNA unwinds and the weak hydrogen bonds between bases break

This means the tow strands separate at a “replication fork” to form two template strands

20
Q

Describe the second stage of the process of DNA replication

A

A primer binds to the 3’end of the template strands. This acts as a starting point for replication as this is where the nucleotides are added to

21
Q

Which strand is replicated in fragments?

A

Lagging strand

22
Q

Which strand is replicated continuously?

A

Leading strand

23
Q

What is the name of the strand with the free 3’end?

A

Leading strand

24
Q

What is the name of the strand with the free 5’end?

A

Lagging strand

25
Q

Describe the third stage of DNA replication

A

Once the primers are in place the enzyme DNA polymerase is able to add complementary DNA nucleotides( through base pairing) from deoxyribose 3’end of the new DNA strand which is forming

26
Q

Describe the fourth stage of DNA replication

A

As DNA can only add nucleotides in one direction the leading strand is replicated continuously and the lagging strand replicated in fragments

27
Q

Describe the fifth stage of DNA replication

A

On the lagging strand many primers bind along the other strand as the replication fork opens the fragments of DNA are then joined together with the help of an enzyme called ligase

28
Q

What is ligase and what does it do?

A

Ligase is an enzyme which allows fragments of DNA to join together on the 5’end strand

29
Q

What is PCR and what does it involve?

A

Polymerase chain reaction(PCR) is used AMPLIFY target sequences of DNA(copy it in the lab)
PCR involves repeated cycles of heating and cooling

30
Q

What does PCR use?

A

Primers

31
Q

What does PCR use primers for?

A

PCR uses primers which are short strands of DNA nucleotides which are complimentary to specific target sequences at the two ends of the region of the DNA to be amplified

32
Q

Describe is the first stage of PCR

A

DNA is heated to between 92 and 98 degrees to separate the two strands(by breaking the hydrogen
bonds between bases)

33
Q

Describe the second stage of PCR

A

It (DNA) is heated to between 50 and 60 degrees to allow primers to bind/anneal

34
Q

Describe the third stage of PCR

A

It (DNA) is then heated to between 70 and 80 degrees for heat tolerant DNA polymerase to replicate the region of DNA

35
Q

Describe the stages of PCR

A
  1. DNA is heated to between 92 and 98 degrees to separate the two strands(by breaking the hydrogen
    bonds between bases)
  2. It is heated to between 50 and 60 degrees to allow primers to bind/anneal
  3. It is then heated to between 70 and 80 degrees for heat tolerant DNA polymerase to replicate the region of DNA
36
Q

What is the end product of PCR and how many times is the process repeated?

A

The product is two identical copies of DNA at the end of the first cycle.
It is repeated many times (20-30) with each cycle doubling the quantity of DNA

37
Q

State the uses of PCR and an example for each

A

MEDICAL- diagnose a disease
- estimate the risk of disease onset

FORENSIC- help solve crimes

PATERNITY
DISPUTES - confirm genetic relationships between individuals

38
Q

What experiment allows DNA fragments to be assessed according to size?

A

Gel electrophoresis separates mixtures of DNA fragments according to size

39
Q

On paternity diagrams can DNA come from the mother or father?

A

Yes

Higher Human (3 decks)

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