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biology gcse > topic 3 - genetics > Flashcards

topic 3 - genetics Flashcards

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1
Q

what are the advantages of sexual reproduction?

A

-produce variation (due to genetic variation)
-survival advantage by natural selection
-> sped up by humans in selective breeding

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2
Q

what are the disadvantages of sexual reproduction?

A

-lots of time and energy needed to find a mate
-not possible for isolated individual to reproduce

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3
Q

what are the advantages of asexual reproduction?

A

-only 1 parent needed -> more energy and time efficient (no wasted gametes)
-more reliable offspring
-identical offspring - can be produced in favourable conditions

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4
Q

what are the disadvantages of asexual reproduction?

A

-doesn’t lead to genetic variation in population
-species may only be suited to 1 habitat
-disease may affect all individuals

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5
Q

what are gametes?

A

sex cells (sperm and egg)

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6
Q

what is a zygote?

A

fertilized egg

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7
Q

what are the stages of mitosis?

A

IPMATC

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8
Q

what is DNA organised into in the nucleus?

A

chromosomes

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9
Q

how many chromosomes do normal body cells have?

A

46 - diploid

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10
Q

how many chromosomes do gametes have?

A

23 - haploid

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11
Q

what is meiosis?

A

type of cell division that results in 2 daughter cells - each with half the number of chromosomes of the parent cells (production of gametes)

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12
Q

describe meiosis?

A

-DNA duplicates
-divides into 2 cells - each have 1 full set of DNA
-cross over occurs - mixes DNA of mother and father
-second division occurs - leaves 4 genetically different daughter cells each with half set of DNA - making them haploid (1n)

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13
Q

how many chromatids are in 2 replicated chromosomes after meiosis?

A

4 sister chromatids

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14
Q

what is meiosis’ role in sexual reproduction and growth of the embryo?

A

-meiosis needed to form gametes
-these fuse to from zygote
-zygote divides by mitosis to form embryo

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15
Q

what is the genome?

A

entire genetic material of an organism

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16
Q

what is a gene?

A

short section of DNA that instructs for a particular protein

17
Q

what is DNA?

A

deoxyribonucleic acid - polymer of nucleotides made up of 2 strands that form a double helix

18
Q

what are the bases of DNA?

A

C, G, A, T

19
Q

what are the pairs of bases?

A

C with G and A with T

20
Q

what is the structure of DNA?

A

-polymer - joined by nucleotides - sugar phosphate backbone
-2 strands coil to form a double helix
-linked by series of complementary bases joined by weak hydrogen bonds

21
Q

what is the hydrogen bonding rule for the base pairs?

A

C bonds to G with 3 hydrogen bonds
A bonds to T with 2 hydrogen bonds

22
Q

how can DNA be extracted from fruit cells?

A
  1. mash strawberries in beaker containing detergent and salt
  2. detergent breaks down cell membranes releasing DNA - salt clumps DNA together
  3. filter mixture to get froth and big insoluble bits of cell out
  4. add ice-cold ethanol slowly stop when as much has been added as there is filtrate
  5. DNA insoluble in cold ethanol so will appear as a stringy white precipitate
23
Q

what does the DNA base sequence code for?

A

sequence of amino acids in the polypeptide chain of a protein which fold to produce specifically shaped proteins (e.g. enzymes)

24
Q

where does protein synthesis occur?

A

ribosomes but DNA is too large to leave nucleus so has to go through transcription

25
Q

what is transcription?

A

where bases in DNA is used to make small, single strand of mRNA

26
Q

what bases does RNA use?

A

C, G, A, U - instead of T

27
Q

describe transcription

A
  1. section of DNA (gene) unwinds and unzips (hydrogen bonds between 2 stands breaks)
  2. RNA nucleotides bind to exposed bases on template strand - RNA polymerase joins
  3. forms mRNA - complementary to template strand + matches coding strand (but RNA)
  4. mRNA leaves nucleus to go to ribosomes
  5. 2 strands of DNA join back up
28
Q

describe translation

A
  1. first mRNA codon is read and a tRNA molecule with complementary anticodon binds bringing the first amino acid
  2. next codon read and tRNA with complementary anti-codon binds with 2nd amino acid - peptide bond forms between amino acids
  3. only 2 tRNA’s can attach at a time so first one leaves and is free to collect another amino acid
  4. chain grows as process continues and ribosome moves down mRNA
  5. polypeptide formed

biology gcse (6 decks)

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