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Term 2 - Yr 11 > Biology - Cell division and genetics > Flashcards

Biology - Cell division and genetics Flashcards

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1
Q

Define DNA

A

the unit of genetic inheritance which is found as chromosomes in the nucleus

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2
Q

How many chromosomes humans have?

A

46 (23pairs)

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3
Q

Where is DNA found in the cell?

A

Nucleus

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4
Q

Define gene

A

a length of DNA that codes for a protein

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5
Q

Define allele

A

a version of a gene

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6
Q

What is the shape of DNA and what is it made of?

A

Double helix; made of two strands of nucleotides forming a twisted ladder.

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7
Q

What are the 3 parts of a DNA nucleotide?

A

Phosphate group, deoxyribose sugar, nitrogenous base.

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8
Q

What forms the DNA backbone?

A

Sugar and phosphate groups.

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9
Q

What are the 4 DNA bases?

A

Adenine (A), Thymine (T), Cytosine (C), Guanine (G).

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10
Q

What holds DNA base pairs together?

A

Hydrogen bonds: A-T (2 hydrogen bonds), C-G (3 hydrogen bonds)

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11
Q

How do the two DNA strands run?

A

Antiparallel (opposite directions).

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12
Q

What is a chromosome?

A

Coiled DNA wrapped around histone proteins

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13
Q

Define gene mutation

A

a change in the base sequence of DNA

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14
Q

What occurs before mitosis?

A

the exact duplication of chromosomes occurs before mitosis

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15
Q

How does DNA control cell function?

A

production of proteins like enzymes.

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16
Q

What is mitosis?

A

Mitosis is cell division that makes two identical daughter cells with the same number of chromosomes.

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17
Q

What happens during mitosis?

A
  1. Interphase - DNA is duplicated
  2. Prophase – Chromosomes condense, nucleus breaks down.
    3.Metaphase – Chromosomes line up in the middle.
    4.Anaphase – Copies of chromosomes are pulled apart to opposite ends.
    5.Telophase – New nuclei form around each set.
    Final step: cytokinesis Cell splits, making two identical cells.
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18
Q

What are the roles of mitosis?

A

Growth, repair, Replacement, Asexual reproduction

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19
Q

What is Protein Synthesis?

A

Protein synthesis is how cells make proteins.

It happens in 2 steps:
→ Transcription (in nucleus)
→ Translation (in ribosome)

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20
Q

What is the transcription stage?

A

Happens in the nucleus.
DNA → mRNA (messenger RNA).
The DNA unzips, and mRNA copies one gene.
mRNA then leaves the nucleus and goes to a ribosome.

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21
Q

What is the translation stage

A

Happens in the ribosome (in the cytoplasm).
mRNA → protein.
tRNA brings amino acids that match the mRNA codons
The amino acids are joined to make a protein chain.

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22
Q

What does mRNA and tRNA stand for?

A

m - messenger
t - transfer

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23
Q

What are mutations caused by and some examples

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A

Caused by mutagens, e.g UV light, X-rays, radiation

24
Q

What is RNA

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A

Is single stranded and has uracil (U)

25
What does haploid mean?
n, 1 sets of chromosomes, gametes
26
What does diploid mean
2n, 2 sets of chromosomes, body cells
27
Describe meiosis
A process of cell or nuclear reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells. Used to produce gametes (sex cells)
28
How does meiosis produce variation?
By forming new combinations of maternal and paternal chromosomes in the gametes.
29
How do you know if your a female / male?
The 23 chromosme, xx - girl, xy - boy
30
What is the crossing over process?
They cross over to exchange DNA. Once crossed over its called recombinant chromatids, if not crossed over, non-recombinant chromatids
31
What is asexual reproduction and some examples?
A type of reproduction where one parent produces genetically identical offspring (clones). No gametes (sex cells) are involved. E.g plants, bacteria, fungi
32
What is sexual reproduction?
A type of reproduction involving two parents and the fusion of gametes, producing genetically different offspring. E.g humans, animals
33
Compare asexual and sexual reproduction.
Asexual: 1 parent, clones, fast Sexual: 2 parents, variation, slower Asexual = good in stable conditions Sexual = better for adaptation
34
Define Genotype
genetic makeup of an organism in terms of the alleles present.
35
Define phenotype
the observable features of an organism.
36
Define dominant
an allele that is always expressed if it is present and that a recessive allele is only expressed when there is no dominant allele of that gene present.
37
Define codominance and describe its genotype and phenotype with examples
neither allele is completely dominant or completely recessive
38
Define homozygous
having two identical alleles of a particular gene (two identical homozygous individuals that breed together will be pure-breeding) and heterozygous as having two different alleles of a particular gene (not pure-breed).
39
What does homozygous and heterozygous look like?
Homozygous - XX Heterzygous - Xx
40
What is the difference between discrete and continuous?
Continuous is number e.g foot size, discrete is a group of things like colours
41
How do you use a genetic diagram to predict the results of a monohybrid cross
Punnet square
42
What is a sex-linked characteristic?
It’s a trait controlled by a gene on the sex chromosomes, usually the X chromosome.
43
Why are sex-linked traits more common in one sex?
Because males (XY) only need one copy of the faulty gene to show the trait, while females (XX) need two copies.
44
What is an example of a sex-linked characteristic?
Colour blindness – it’s more common in males.
45
What is a pedigree chart?
A diagram showing inheritance of a trait through a family (like a family tree).
46
What symbols are used in pedigree charts?
Circle = female, Square = male Shaded = affected, Unshaded = unaffected
47
What are the two types of variation?
Genotypic variation – caused by differences in genes Phenotypic variation – caused by genes + environmental factors
48
What is variation?
differences between individuals of the same species and recognise phenotypic and genotypic variation (including that phenotypic variation is caused by both genetic and environmental factors).
49
What causes phenotypic variation?
both genetic factors (inherited genes) and environmental factors (like diet, lifestyle, etc.)
50
What is discontinuous variation?
mostly caused by genes alone, e.g blood group, toungue rolling ( use bar chart)
51
What is continuous variation?
Variation that shows a range of phenotypes between two extremes, usually caused by genes and environment.e.g height, weight ( use line graph )
52
What is natural selection?
Natural selection is the process where individuals with variations better suited to the environment survive, reproduce, and pass on their alleles to the next generation.
53
What factors are involved in natural selection?
Variation, many offspring, competition, struggle for survival, reproduction of better-adapted individuals, and passing on alleles.
54
What are adaptive features?
Inherited traits that increase an organism’s chance of survival and reproduction (fitness).
55
Give examples of adaptive features in desert species.
Fennec fox: big ears for cooling. Camel: stores fat in hump. Cactus: thick stem and spines to store water and reduce loss.
56
What is evolution?
A change in the adaptive features of a population over time.
57
What is the difference between natural and artificial selection?
Natural: nature selects traits. Artificial: humans select traits through selective breeding.

Term 2 - Yr 11 (6 decks)

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