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Biology > genetics and reproduction P2 > Flashcards

genetics and reproduction P2 Flashcards

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1
Q

Sexual reproduction

A

Meiosis

  • 2 parents needed
  • fusion of male and female gametes to create a zygote (fertilized egg)
  • offspring produced is genetically different
  • mixing of genetic information
  • chromosomes are halved (23)
  • divides twice
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2
Q

Asexual reproduction + examples

A

Mitosis

  • involves only one individual
  • offspring is genetically identical to parent
  • no fusion of gametes or mixing of genetic information

= aphids, buds

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3
Q

Zygote

A

a fertilized egg

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4
Q

Mitosis + uses

A

1) nucleus with 46 chromosomes in
2) DNA replication and cell growth;
chromosomes copied (and everything else in cell), nuclear membrane breaks down
3) Mitosis; chromosomes and copies pulled apart and moved towards poles
4) Cell division; cell divides into two genetically identical daughter cells

-uses of mitosis; growth, repair of damaged tissues, replacement of worn out cells

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5
Q

Gamete

A

A sex cell (egg, sperm)

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6
Q

DNA structure

A

DNA is a polymer made up of two twisted ladder structures called the double helix.
DNA is found in the chromosomes in the nucleus of an organism.
It is our genetic material which determines our inherited features.

DNA is a polymer of molecules called nucleotides (3 parts, phosphate group attached to sugar molecule, attached to a base) —> only base changes

Bases : ACGT -> DNA contains 4 nucleotides
DNA strands are complementary as the same bases always pair on the opposite strands.

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7
Q

Gene

A

A small section of DNA on a chromosome

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8
Q

Genome

A

The entire genetic material of an organism

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9
Q

Why is it important to understand the human genome? (benefits)

A

1) Helps us understand and treat inherited diseases (e.g cystic fibrosis)
2) Helps us to search for genes that are linked to a disease (e.g genes that increase the risk of developing cancer).
3) Can use human genome to trace human migration patterns from the past —> helps with understanding ancestory

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10
Q

What does it mean when saying DNA strands are complementary?

A

Means that same bases always pair on the opposite strands.
C-G
A-T

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11
Q

Protein Synthesis

A

1) Takes place in nucleus, Transcription -> Base sequence of gene is copied into a complementary template molecule called the messenger RNA ( a single stranded molecule)

mRNA now passes out of nucleus and into cytoplasm

2) Takes place in cytoplasm, Translation ->
- mRNA molecule attaches to a ribosome
- amino acids are brought to ribosome on carrier molecules, called transfer RNA
- ribosome reads the triplets of bases on mRNA and uses this to bind the correct amino acids in the right order
- once protein chain is complete, folds out into its unique shape for its specific job

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12
Q

nucleotide

A 
a monomer (single unit) of DNA 
(consists of phosphate, sugar and base)
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13
Q

Amino acids

A

-what makes up proteins

a group of 3 bases codes for an amino acid ( TAG or CTA or TGC)

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14
Q

Chromosome

A

Long threads of DNA , which are made up of many genes (contains the DNA)

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15
Q

haploid

A

a cell that contains a single set of chromosomes (e.g a gamete)

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16
Q

diploid

A

a cell that contains the full 23 chromosome pairs (e.g a human cell)

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17
Q

fertilisation

A

fusion of female and male gametes

=in fertilisation cells restore the full normal amount of chromosomes (opposite to meiosis)

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18
Q

meiosis

A

Takes place in reproductive organs (testes, ovaries)
-sexual reproduction

1) chromosomes in human reproductive organ are copied
2) cell divides into two
3) cell divides again to from 4 gametes which contain single chromosomes (not paired)
4) these gametes contain half the amount of chromosomes (23) so that when fertilisation occurs, it restores the normal amount of 46

  • meiosis halves the amount of chromosomes
  • produces 4 gametes from one cell
  • all 4 gametes are GENETICALLY DIFFERENT
19
Q

how many amino acids are there in a human?

A

20

20
Q

order of amino acids

A

The specific order of an amino acid determines its shape and function.
The order of amino acids in a protein is determined by the sequence of bases in the gene.

21
Q

what is a mutation

A

a change in a base

- they happen all the time

22
Q

ineffective mutation

A

A single base in a sequence changes (mutation occured) but amino acid has not changed the sequence. This is because different base triplets can encode for the same amino acid . So in this case the mutation has had no effect.
= most mutations are ineffective and happen frequently

23
Q

effective mutation

A

A single base in a sequence changes (mutates) and the amino acid changes and this change has altered the shape and function of protein.
= could lead to the active site changing so the substrate no longer fits

24
Q

chromosomes also contain non-coding parts of DNA + mutation

A

These regions switch genes on and off. This means they tell genes when to produce proteins.
Mutations in these regions can affect how the gene is switched on and off (e.g a gene may be turned on when it should be off. In this case, the cell would produce a protein that was not needed at that time). –> uncontrolled mitosis leading to cancer

25
Q

where is dna found

A

in chromosomes

26
Q

alleles

A

different versions of the same gene

27
Q

genotype

A

refers to the combination of alleles an organism has ( BB, bb, Bb)

28
Q

homozygous

A

two copies of the SAME allele (EE) or (ee)

29
Q

phenotype

A

tells us the physical characteristics caused by the persons alleles
(e.g two alleles for dry ear wax ee = phenotype is dry ear wax)

30
Q

heterozygous

A

two DIFFERENT alleles ( Ee)

31
Q

dominant alleles

A

capital letter

- will show in the phenotype even if there is only one copy (e.g Ee)

32
Q

recessive alleles

A

lower case letter

= must be two copies to be shown in phenotype (ee) not (Ee)

33
Q

cystic fibrosis , what is it?

A

An inherited disorder of the cell membranes in the lungs. Abnormally thick mucus.

  • recessive allele (must have two recessive alleles to have it)
  • can be a carrier
34
Q

carrier

A

someone who can pass a disease onto their children but they are healthy
someone who can pass a disease onto their children but if a person has 1 of each allele (heterozygous) they are a carrier

35
Q

can you be a carrier of a disease caused by a dominant allele?

A

NO - because dominant alleles are expressed even if there is only one.

36
Q

Polydactyly

A

An inherited disease which causes extra toes/fingers.

- caused by a dominant allele, cannot be a carrier

37
Q

solutions for inherited diseases?

A

embryo screening - embryos are tested to see if they possess the alleles for inherited disorders. If they do not then they are implanted into the women to produce healthy offspring. (form of genome screening)

38
Q

advantages and disadvantages of embryo screening

A

disadvantages ->

  • ethical issues as embryo cannot give consent/often loads of a embryos are tested those that are not (although perfectly healthy) are destroyed.
  • expensive
  • parents become selective -> technology could allow parents to chose the most desirable embryo

advantages ->

  • prevents suffering of offspring with genetic disorders
  • financial saving (less people with inherited diseases, less money on treatment, better in long-term)
39
Q

cystic fibrosis : CC , Cc, cc meaning

A

CC -> not affected
Cc -> carrier
cc-> affected

40
Q

polydactyly: PP, Pp , pp meaning

A

PP -> affected
Pp -> affected
pp -> not affected

41
Q

what do family trees show/not show

A

they show the phenotype NOT the genotype

42
Q

vector

A

transfering DNA from one organism to another

43
Q

Genetic Engineering

A

1) Identify the gene you want to transfer (e.g human gene or plant gene)
2) Use enzymes to isolate this gene
3) Transfer gene into a plasmid or a virus (vector : transfers dna from one organism to another)
4) Desired gene is transferred into the cells of the target organism (idea is that the organisms cells will take up the vectors, and the useful gene inside it, to produce the protein that the gene codes for)

(always transfer a gene at the early stage in the organisms development = to make sure all cells recieve the transferred gene, so develops with the desired characteristics)

Biology (10 decks)

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