3.1.7 DNA, Genes & Chromosomes Flashcards Preview

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Flashcards in 3.1.7 DNA, Genes & Chromosomes Deck (57)
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1

What is the basic function of DNA?

Used to store genetic information

(all instructions organism needs to grow and develop from fertilised egg to adult)

2

What is the main function of RNA?

Transfer genetic information from DNA to ribosomes

3

What do ribosomes (AKA body's 'protein factories') do?

Read RNA to make polypeptides in process called translation

4

What are ribosomes made from?

RNA and proteins

5

What 3 things does a nucleotide consist of?

  • Nitrogen-containing organic base
  • Pentose sugar
  • Phosphate group 

6

What are monomers that make up DNA & RNA?

Nucleotides

7

How are polynucleotides formed?

  • Nucleotides join via condensation reaction between phosphate group of one nucleotide and sugar of another
  • This forms a phosphodiester bond

8

What is a chain of sugar and phosphates called?

Sugar-phosphate backbone

9

What is the pentose sugar in a DNA nucleotide?

Deoxyribose

10

Each DNA nucleotide has same sugar & phosphate group but a different ___

base

11

Name the 4 possible bases in a DNA nucleotide

  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)

12

What is the pentose sugar in a RNA nucleotide?

Ribose

13

Name the 4 possible bases in a RNA nucleotide

  • Adenine (A)
  • Uracil (U)
  • Cytosine (C)
  • Guanine (G)

14

Describe how the structure of DNA is formed

  1. 2 DNA polynucleotide strands join together by hydrogen bonding between complementary base pairs
  2. 2 hydrogen bonds form between A & T, and 3 hydrogen bonds form between C & G
  3.  2 antiparallel polynucleotide strands twist to form DNA double-helix

15

What does adenine pair with?

Thymine (A - T)

16

What does cytosine pair with?

guanine (C - G)

17

There is always _____ amounts of A & T in DNA molecule and C & G

EQUAL

18

Ratio of A & T to G & C varies from...

species to species

19

Describe the structure of RNA

Made from single polynucleotide chain = much shorter than most DNA polynucleotides

20

Name the 3 Types of RNA in every cell

  • tRNA
  • rRNA
  • mRNA

21

What does rRNA do?

Type of RNA that makes up ribosomes

22

Explain how the structure of DNA is related to its functions (6)

  1. Double helix protects bases from corruption
  2. Large molecule so can store lots of genetic information
  3. Helix/coiled so compact
  4. Double stranded so replication can occur semi-conservatively
  5. (Weak) H-bonds for replication
  6. Many H-bonds so stable
  7. Complementary base pairing so accurate identical copies can be made
  8. Base sequence allows information to be stored

23

Explain why the replication of DNA is described as semi-conservative (2)

  • Each strand copied / acts as a template 
  • DNA has one new strand & one orginial

24

Describe stage 1 of semi-conservative replication

DNA helicase breaks H bonds between bases = backbone is unzipped = helix unwinds

25

Describe stage 2 of semi-conservative replication

Each original single strand acts as template for new strand:

Free nucleotides are attached to their complementary base on the backbone (orginal strand)

26

Describe stage 3 of semi-conservative replication

  • Condensation reactions join nucleotides - catalysed by enzyme DNA polymerase
  • H bonds form between bases (on original and new strands)

27

Describe stage 4 of semi-conservative replication

Each new DNA molecule contains one strand from original DNA molecule and one new strand

(Double strand twists again)

28

______ Eukaryotic DNA is _____ & ______ with ______

Nuclear Eukaryotic DNA is Linear & Associated with Proteins

29

What is a DNA molecule in eukaryotic cells wound around?

(Proteins called) histones

30

What do histone proteins do?

Help support the DNA

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