Biology GCSE > Genetics > Flashcards

Genetics Flashcards

(57 cards)

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1
Q

define diploid

A

cell that has normal number of chromosomes (46 in humans)

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2
Q

define haploid

A

cell that has half the normal number of chromosomes (23 in humans). also known as gametes/sex cells

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3
Q

what is the key difference between mitosis and meiosis?

A

the cells divide a second time without duplicating chromosomes, producing 4 haploid daughter cells rather than 2 diploid daughter cells

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4
Q

why is meiosis needed for reproduction?

A

to produce cells with half the normal number of chromosomes (haploid, 23 in humans)), so when it fuses with another gamete (egg in humans) it has the normal number of chromosomes (46), as if two diploid cells fused they would not be viable (as it has 92 chromosomes)

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5
Q

meiosis process?

A

diagram in book 2 page 42

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6
Q

does genetic variation occur in mitosis or meiosis?

A

meiosis

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7
Q

why is genetic variation needed?

A

so parents and offspring are not genetically identical
if a disease struck, some individuals may have the traits to survive, if all are genetically identical, whole species may go extinct.

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8
Q

female gamete in animals?

A

egg cell (ovum)

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9
Q

male gamete in animals?

A

sperm

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10
Q

male gamete in plants?

A

pollen

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11
Q

female gamete in plants?

A

egg cells (ovum)

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12
Q

pros and cons on sexual reproduction?

A

Pros
- inherited diseases have chance of not being passed on due to genetic diversity
- variation gives resistance against disease/ change in envir.
- can be used by humans for selective breeding in agriculture

Cons
- inherited diseases can be passed on
- beneficial characteristics from prev. gen. may be lost
- risky for species survival as relies on finding a partner
- energy intense

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13
Q

describe the features of asexual reproduction?

A
  • 1 parent
  • cells divide by budding/mitosis/binary fission
  • no fusion of gametes
  • common in small animals and plants, bacteria and fungi
  • bulbs and runners are clones
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14
Q

how do fungi reproduce?

A

both asexually and sexually
- reproducing spores is asexual
- hyphae touching and sharing genetic info is sexual

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15
Q

what are genes?

A

subsections of DNA

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16
Q

what are chromosomes made up of?

A

DNA

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17
Q

describe the structure of DNA

A
  • double helix structure
  • is a polymer; a chain of repeating monomers
  • has a sugar phosphate backbone
  • nitrogenous base pairs (joined by hydrogen bonds) make up the ‘rungs’
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18
Q

describe what a nucleotide is and it’s structure

A
  • is one section of the DNA which is repeated over and over
  • made of a sugar (pentagon), bonded to a phosphate(circle) on the upper left and a base (square) to the right
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19
Q

which bases bond with which?

A

A bonds with T (straight letters)
C bonds with G (curvy letters)

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20
Q

what is all of the DNA of an organism called?

A

the genome

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21
Q

what was the human genome project?

A

project in 1986 to sequence the entire human genome

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22
Q

aims of human genome project?

A
  • sequence entire human genome
  • identify human genes
  • create databases for data storage
  • address ethical, legal and social issues
  • understand function of genes
  • create a physical map of human genome
  • identify disease causing genes
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23
Q

causes for and against the human genome project?

Study These Flashcards
A

for
- advance scientific understanding
- help understand health risks and develop new treatments
- provided jobs and money

against
- genetic discrimination and social inequality
- privacy, consent, commercialisation and data storage
- gene editing

24
Q

what are the two main parts of protein synthesis?

Study These Flashcards
A

transcription - DNA transcribed into mRNA
translation - mRNA is translated into an amino acid sequence

25
what is different about pairing of bases in protein synthesis?
A bonds with U instead of T, and when it is transcribed, U bonds to A
26
describe the process of transcription
- DNA helicase unzips small part of DNA, exposing only gene that needs transcribing - complementary RNA nucleotides line up against DNA template strand - single stranded copy of DNA called mRNA is made. Only made for the genes we need, not whole DNA strand - mRNA is released from DNA and DNA reforms double helix - mRNA leaves nucleus through nucleic pores and moves to ribosome in cytoplasm
27
describe process of translation
- mRNA binds to ribosomes - ribosome reads mRNA in groups of 3 (triplets). 3 bases code for 1 amino acid - carrier molecules (tRNA) with complementary base sequence to triplet bond to mRNA at ribosome. Attached to other end is an amino acid - next triplet read and process continues - Peptide bond forms between amino acids, and first tRNA can leave. Chain is forming - third triplet read, chain grows etc. - once all mRNA read, a sequence of amino acid s is left, known as a polypeptide chain (protein)
28
which bits of DNA do not code for proteins and what do they do?
- Introns - can act as switches to turn on or off sequences
29
what are the sections of DNA that code for proteins called?
Exons
30
what happens to Introns and Exons during transcriptions?
- both are transcribed - introns removed from initial transcript - exons spliced together to form final transcript - mRNA leaves nucleus
31
what are mutations?
- a change to DNA (change to base sequence) - can happen spontaneously or be caused by different factors
32
what is variation?
differences between members of the same species
33
what are the three main types of mutagens, and examples
- Radiation, like UV radiation and x-rays - Chemicals, like cigarette smoke, nitrate preservatives, barbecuing - Infectious agents, like HPV and Heliobacter Pylori
34
are mutations always bad for individual/ species
no, eg. resistant bacteria is more likely to survive
35
what is sickle cell anaemia?
- a disease primarily affecting Afro-Caribbean people, where due to GTA being coded instead GAA, valine is produced instead of glycolic acid, resulting in sickle shaped RBCs - this means they carry less oxygen and can get stuck in vessels, but prevents them from getting malaria
36
what is a silent mutation?
when a base is changed in the DNA is changed, but it still codes for the same protein, meaning the end result is still the same
37
a mutation in an exon may lead to....
- DNA base sequence changed, different amino acid coded for so different protein - mutation makes a stop signal, so protein is shortened and doesn't function - if occurs in a body cell, cancer may occur - if in egg/sperm, offspring may have a genetic disorder - if in enzyme, active site shape may be altered and no longer works
38
how does a mutation lead to an enzyme not functioning?
- different protein produced - not folded correctly - alters intermolecular forces holding 3D shape - active site shape altered - doesn't catalyse
39
what may be caused by a mutation in an intron?
- may turn on or off gene when not needed, resulting in: - protein being unnecessarily produced, wasting energy - lack of protein being produced when needed
40
define gene
a section of DNA which codes for characteristics
41
define allele
the different forms of a gene
42
define phenotype
physical appearance of an organism
43
define genotype
the set of genes (alleles) than an organism possesses (genotype causes phenotype)
44
define homozygous
when two alleles are identical
45
define heterozygous
when two alleles are different
46
define dominant (freak...)
an allele which always controls the characteristic when it is present
47
define recessive
an allele whose characteristics only show up when it is present on both chromosomes
48
how are dominant and recessive represented as letters?
Dominant = BB (capitals) Recessive = bb (lowercase) -> can be other letters
49
what do you need to gain full marks on a question about calculating ratio of inherited phenotypes probability?
- parents phenotypes and genotypes - genotypes of all offspring - offspring phenotypes and genotypes matched correctly - ratio or probability
50
what is needed to go with a punnett square?
a key matching allele with expressed phenotype
51
what is polydactlyly?
- being born with multiple fingers or toes - passed down through a dominant gene - can be lived with, but some people choose to remove extra digits - doesn't change throughout life
52
what is cystic fibrosis?
- disorder where mucus made by cells becomes very sticky and thick, organs can be clogged by buildups - movement of certain substances can be very difficult - pancreas can't secrete enzymes properly, tube to intestine blocked - caused by a recessive allele
53
treatments for cystic fibrosis?
- physiotherapy and antibiotics to keep lungs clear - enzymes to replace ones from pancreas
54
two methods of screening embryos?
- amniocentesis - chorionic villus
55
what is amniocentesis?
- extracting fluid from foetus which contains foetal cells which can be used for screening - around 15-16 weeks
56
what is chorionic villus?
- sampling of embryonic cells by taking tissue sample from placenta - around 10-12 weeks
57
concerns about embryo screening?
- risk of miscarriage, plus is an invasive procedure - expensive - ethical objections (religious, designer babies) - distressing to choose whether to terminate embryos or not
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