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GCSE Biology > SB3 > Flashcards

SB3 Flashcards

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1
Q

What is a clone

A

A genetically identical offspring to the parent

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2
Q

List advantages of asexual reproduction

A
  • Faster than sexual reproduction
  • One parent is needed
  • Population can increase rapidly
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3
Q

List advantages of sexual reproduction

A
  • Provide variation (greater chance that offspring will be better suited to new conditions)
  • A disease is less likely to harm the entire population
  • Species can begin to adapt
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4
Q

What is a genome

A

The DNA of an organism

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5
Q

What does meiosis do

A

It produces gametes/haploid cells (genetically different)

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6
Q

Explain meiosis

A

Each chromosome replicates
The two sets of chromosomes pair up then separate into two new cells
The two copies of chromosomes split into two again, creating two more new cells
This creates four genetically different haploid daughter cells

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7
Q

What shape is DNA

A

Double helix

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8
Q

What are the four DNA bases

A

Cytosine, guanine, adenine and thymine

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9
Q

Why does cytosine only pair with guanine

A

Cytosine and guanine form 3 hydrogen bonds whereas adenine and thymine only form 2. (Hydrogen bonds are what are formed when a slightly charged part of a base is slightly attracted to another base)

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10
Q

What happens in transcription

A

RNA polymerase (an enzyme) attaches to DNA in front of a gene in the non-coding region
Enzyme separates the two DNA strands
The enzyme moves along the DNA strand and adds the complementary bases (instead of thymine it uses uracil)
This forms a strand of mRNA

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11
Q

What happens in translation

A

mRNA travels out of the nucleus through nuclear pores into the cytoplasm
The mRNA attaches to ribosomes
The ribosomes move along the mRNA strand 3 bases at a time (called triplet)
Each triplet is called a codon
At each mRNA codon, a tRNA molecule lines up and carries an amino acid
As the ribosome moves along, a polypeptide chain is formed from the amino acids

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12
Q

What happens to the polypeptide chain

A

It folds to create a protein with a specific shape

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13
Q

What does genetic code actually code for

A

How the base order in DNA or RNA is turned into a protein

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14
Q

What is phenotype

A

Observable characteristics

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15
Q

How are mutations caused

A

A change in the bases of a gene when DNA is not copied properly in cell division or uncontrollable cell division. Environmental factors can also cause mutation

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16
Q

How are mutations caused in non-coding regions

A

RNA polymerase not binding well, reducing transcription

17
Q

What are alleles

A

Different versions of the same gene

18
Q

Why do gametes only have one copy of each gene

A

Because they have one copy of each chromosome and need half the full number of chromosomes to fuse with another gamete to produce a cell with the full amount

19
Q

What is genotype

A

The alleles in an organism

20
Q

What gamete is responsible for determining the sex of the offspring

A

Sperm cell (X for female, Y for male)

21
Q

What are the four blood groups

A

A, B, AB, O

22
Q

What is codominance

A

When both alleles for a gene affect the phenotype

23
Q

How can mapping a person’s genome be useful

A

It can tell us their risks of developing diseases caused by different alleles
It can also help tell us what medicines would be best for them (alleles can affect the way medicine works for us)

24
Q

Why is genetic variation caused

A

The different alleles being inherited during sexual reproduction

25
Q

What are acquired characteristics

A

Characteristics that are changed by the environment during life

26
Q

What is discontinuous variation

A

Data that can only take a limited set of values (eg: eye colour, it cannot change)

27
Q

What is continuous variation

A

Data that can be any value in a range (changeable characteristics such as height)

GCSE Biology (9 decks)

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