Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

biology year 1 > diversity and selection B > Flashcards

diversity and selection B Flashcards

1
Q

what is meant by the term haploid

A

haploid means there is one copy of each chromosome in the nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is meant by the terms diploid

A

diploid means there are two copies of each chromosomes in the nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

state how zygotes are formed and whether they are haploid or diploid

A

formed by fusion of two haploid gametes during fertilisation. this makes zygotes diploid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are mutagenic agents

A

factor that increases the rate of mutation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

state the difference between mitosis and meiosis

A

MITOSIS
-produces two genetically identical daughter cells
-parent cell is diploid, daughter cells are diploid
-one division
-no separation of homologous chromosomes
-used for growth and repair of tissues
MEIOSIS
-produces four genetically different daughter cells
-parent cell is diploid,daughter cells are haploid
-two divisions
-homologous chromosomes are separated
-used to produce haploid gametes in reproductive organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what happens in Meiosis l (first division)

A

-homologous chromosomes associate (pair up)
-crossing over between homologous chromosomes
-independent segregation of homologous chromosomes
-two haploid daughter cells are produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what happens in Meiosis ll (second division)

A

-chromatids are separated
-four haploid daughter cells are produced that are genetically varied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the importance of meiosis

A
  • Two divisions – creates haploid gametes (half number of chromosomes)
  • Diploid number restored at fertilisation
  • Maintains chromosome number from one generation to the next
  • Independent segregation and crossing over creates genetic variation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how does meiosis create genetic variation

A
  • Crossing over between homologous chromosomes
  • Independent segregation of homologous chromosomes
  • Random fertilisation when two gametes fuse to form a zygote
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is crossing over

A

-regions of non-sister chromatids are exchanged within homologous pairs
-alleles are swapped so new combinations of alleles are produced and the base sequence of chromosomes is altered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

during which division does crossing over take place in

A

first division of meiosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the chiasma

A

the point where non sister chromatids cross when they twist together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is independent segregation

A
  • Random alignment of homologous pairs at equator → random which chromosome from each pair goes to each daughter cell
  • Creates different combinations of maternal and paternal chromosomes and alleles in daughter cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is random fertilisation

A

-produces new combinations of alleles
-fusing of the egg and sperm cells is a random process
-many possible combinations of alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

during sexual reproduction, fertilisation between gametes is random. explain how this could lead to an increased genetic diversity within species .

A

-produces zygotes with different combination of chromosomes to both parents
-this mixing of genetic material increases genetic diversity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is chromosome non-disjunction

A
  • Homologous chromosomes fail to separate during meiosis I OR sister chromatids fail to separate during meiosis II
  • One gamete has an extra copy of this chromosome and the other has none
  • Upon fertilisation, zygote has one fewer (dies) or one extra chromosome (survives)
  • Arises spontaneously
  • Causes genetic diseases e.g. down’s syndrome in humans – extra copy of chromosome 21
17
Q

what is a gene mutation

A
  • A change in the base sequence of DNA (on chromosomes)
  • Can arise spontaneously during DNA replication (interphase)
  • Involves base deletion / substitution
18
Q

when are mutations likely to occur?

A

mutations are most likely to occur during DNA replication

19
Q

how can a mutation lead to the production of a non-functional protein/enzyme

A
  • Change in base / triplet sequence of DNA / gene
  • Changes sequence of codons on mRNA
  • Changes sequence of amino acids in the primary structure of the polypeptide
  • Changes position of hydrogen / ionic / disulphide bonds in tertiary structure of protein
  • Changes tertiary structure / shape of the protein (and active site if enzyme)
  • (if enzyme) substrate can’t bind to active site and form an enzyme-substrate complex
    -can cause a frameshift
20
Q

what is base deletion and what can it change

A
  • One nucleotide / base removed from DNA sequence
  • Changes triplet / codon sequence from the point of mutation (frameshift)
  • Changes sequence of codons on mRNA after point of mutation
  • Changes sequence of amino acids in primary structure of polypeptide
  • Changes position of hydrogen / ionic / disulphide bonds in tertiary structure of protein
  • Changes tertiary structure / shape of protein i.e. non-functional or new and superior
21
Q

what is base substitution and what are the outcomes of it

A
  • Nucleotide / base in DNA replaced with another nucleotide / base
  • Change in one base → changes one triplet
    1. Changes one mRNA codon and one amino acid → sequence of amino acids in primary structure
    of polypeptide changes etc.
    2. Due to the degenerate nature of the genetic code, the new triplet may still code for the same amino acid so the sequence of amino acids in the primary structure of the polypeptide remains unchanged
22
Q

why are deletion mutations more significant than substitution mutations

A

-deletions always lead to changes in the amino acid sequence and substitutions dont
-deletions also usually result in several amino acids being changed rather than just one

23
Q

what is genetic diversity

A
  • Number of different alleles of a gene in a population
    -arises through mutations or meiosis
    -allows natural selection to occur
24
Q

give two ways in which the genetic diversity of a population might increase

A

may increase through mutations creating new alleles or migrations introducing new alleles from other populations

25
Q

genetic diversity can be investigated by comparing….

A

-measurable or observable characteristics
-the base sequence of DNA (looking for mutations)
-the base sequence of RNA
-the amino acid sequence of proteins

26
Q

what are the principles of natural selection in the evolution of populations

A
  1. Variation of alleles exists in population due to random DNA mutations
  2. Selection pressure / change in environment
  3. Those with advantageous allele have increased chance of survival and reproduction – differential survival/reproductive success
  4. Those reproducing pass advantageous allele to offspring
  5. Frequency of advantageous allele and characteristic increases in the population
  6. Over many generations / long period of time
    (evolution: change in allele frequency over time)
27
Q

what is meant by the term adaptation

A

characteristic that increase an organism’s chance of survival (and so reproduction)

28
Q

what are the three types of adaptions

A

-anatomical =Structural features of organisms body / observed structures
-physiological=Processes inside the body
-behavioural =Ways an organism acts

29
Q

what are the two types of selection

A

-directional selection
-stabilising selection

30
Q

directional selection (antibiotic resistance in bacteria)

A

-Change to the environment
-Selection pressure acts one side of the mean
-One extreme phenotype more likely to survive and produce
-Mean phenotype changes

31
Q

stabilising selection (human birth weights)

A
  • Stable environment
  • Selection pressure acts either side of the mean
  • Both extremes of phenotype less likely to survive and reproduce
  • Mean phenotype remains the same
32
Q

why would natural selection be unable to act on a population of cloned (genetically identical) individuals

A

-natural selection requires genetic variation to cause differential reproductive success in a population
- there is no genetic variation in genetically identical population
-therefore natural selection cant happen

biology year 1 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions