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Biology > Topic 3 - Genetics > Flashcards

Topic 3 - Genetics Flashcards

(63 cards)

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1
Q

What is sexual reproduction

A
  • Type of reproduction
  • Involves production of gametes by meiosis
  • Gamete from each parent fuses to form zygote
  • Genetic information from each gamete is mixed so zygote is unique
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2
Q

What are gametes

A
  • Sex cells (sperm cells, egg cells)
  • Gametes are haploid (Half number of chromosomes)
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3
Q

What is meiosis

A
  • Production of 4 daughter cells each with half number of chromosomes
  • Results in formation of genetically different haploid gametes
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4
Q

Why is meiosis important for sexual reproduction

A
  • Increases genetic variation
  • Ensures resultant zygote is diploid
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5
Q

What must occur prior to meiosis

A

Interphase

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6
Q

What is advantage of sexual reproduction

A
  • Creates genetic variation, increasing probability of species adapting to and surviving environmental changes
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7
Q

What are the disadvantages of sexual reproduction

A
  • Two parents are required. Makes reproduction difficult in endangered populations or in species which exhibit solitary lifestyles
  • More time and energy required so fewer offspring are produced
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8
Q

What is asexual reproduction

A
  • Type of reproduction
  • Involves mitosis
  • Produces genetically identical offspring known as daughter cells
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9
Q

What are advantages of asexual reproduction

A
  • Only one parent required
  • Lots of offspring can be produced in short period of time, enabling the rapid colonisation of area reducing competition from other species
  • Requires less energy
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10
Q

What is disadvantage of asexual reproduction

A
  • No genetic mutation in population reducing probability of species being able to adapt to environmental change
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11
Q

What is DNA

A

A polymer made up of:
* Two strands coiled to form a double helix
* Strands linked by series of complemenrary nase pairs joined together by weak hydrogen bonds
* Nucleotides that consist of sugar and phosphate group with one of four different bases attached to the sugar

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12
Q

What is a genome

A

Entire DNA of organism

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13
Q

What is a gene

A

Section of DNA molecule that codes for specific protein

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14
Q

How can DNA be extracted from fruit

A
  1. Place piece of fruit in beaker and crush it
  2. Add detergent and salt, mix them
  3. Filter mixture and collect liquid in test tube
  4. Pour chilled ethanol into test tube
  5. DNA precipitates froming fibrous white solid
  6. Use glass rod to collect DNA sample
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15
Q

Why is detergent added to the crushed fruit

When extracting DNA from a fruit

A

Disrupts cell membranes releasing DNA into solution

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16
Q

Why is salt added to crushed fruit

When extracting DNA from a fruit

A

Encourages precipitation of DNA

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17
Q

Why is chilled ethanol added rather than water

When extracting DNA from a fruit

A

DNA is insoluble in ethanol encouraging its precipitation

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18
Q

Explain how a gene codes for a protein

A
  • Sequence of three bases in a gene form triplet
  • Each triplet codes for an amino acid
  • Order of amino acids determines structure (how it will fold) and function of protein formed
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19
Q

Why is folding of amino acids important in proteins such as enzymes

A

Determines shape of active site which must be highly specific to shape of its substrate

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20
Q

What is protein synthesis

A

Formation of a protein from a gene

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21
Q

What are the two stages of protein synthesis

A
  1. Transcription
  2. Translation
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22
Q

What is the difference between mRNA and DNA

A
  • mRNA is single stranded whereas DNA is double stranded
  • mRNA uses U whereas DNA uses T
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23
Q

Describe translation

A
  • mRNA leaves nucleus and enters cytoplasm
  • Rinosome attaches to mRNA
  • Each tRNA is attached to one specific amino acid
  • tRNA brings specific amino acid to ribosome/mRNA
  • Anticodons on tRNA lines up along codons on mRNA through complementary base pairing (hydrogen bonds)
  • Formation of peptide bond netween adjacent amino acids
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24
Q

Describe transcription

A
  • Transcription occurs in the nucleus
  • RNA polymerase binds to non-coding DNA located in front of a gene
  • RNA polymerase produces complementart mRNA strand from coding DNA of gene
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25
Why is mRNA used in translation rather than DNA
DNA is too large to leave nucleus so can't reach ribosome
26
What is non-coding DNA
DNA which does not code for protein but instead controls gene expression
27
How is tRNA adapted to its function
EAch tRNA molecule has anticodon which is specific to codon of amino acid that it carries
28
What is a mutation
Random change in base sequence of DNA which results in genetic variants
29
Describe effect of gene mutation in coding DNA
* If mutation changes amino acid sequence, protein structure and function may change * If mutation does not change amino acid sequence, there is no effect on protein structure or function
30
What is the effect of a gene mutation in non-coding DNA
* Mutation may affect ability of RNA polymerase to bind to non-coding DNA * Mau affect protein production resulting phenotype of organism
31
How did the work of Gregor Mendel help scientists develop their understanding of genetics
* Studied inheritance of different phenotypes of pea plants * Established correlation between parent and offspring phenotypes * Noted inheritance was determined by 'units' passed on to descendants * Using gene crosses, he devised the terms 'dominant' and 'recessuve'
32
Why was Mendel's work initially overlooked
Scientists didn't understand Mendel's work as there was no knowledge of genes or DNA at the time
33
What is a chromosome
Long, coiled molecule of DNA that carries genetic information in form of genes
34
What is gene
Section of DNA that codes for specific sequence of amino acids which undergo polymerisation to form protein
35
What are alleles
Different versions of same gene
36
What is genotype
Organism's genetic composition, describes all alleles
37
What is phenotype
Organism observable characteristics due to interactions of genotype and environment (which can modify phenotype)
38
What s homozygous
Having two identical alleles of a gene e.g. FF or ff
39
What is heterozygous
Having two different alleles of gene e.g. Ff
40
What is dominant allele
* Describes an allele that is always expressed * Represented with capital letter e.g. F
41
What is a recesskve allele
* Allele that is only expressed in absence of dominant allele * Represented with small letter e.g. f
42
What is monohybrid inheritance
Inheritance of a single gene
43
What are sex chromosomes
Pair of chromosomes that determine sex: * Males have an X and Y chromosome * Females have two X chromosomes
44
Why does inheritance of Y chromosome mean embryo will develop into male
Testes development in embryo is stimulated by gene present on Y chromosome
45
What are ways monohybrid inheritance can be represented
* Punnet square * Family pedigree
46
What is a sex-linked characteristic
Characteristic that is coded for by an alle found on sex chromosome
47
Why are majority of genes found on X chromosome rather than Y chromosome
X chromosome is bigger than Y chromosome so more genes are carried on it
48
Why are men more likely to show phenotype for recessive sex-linked trait than women
* Many genes found on X chromosome that have no counterpart on Y chromosome * Women (XX) have two alleles for each sex-linked gene whereas men (XY) often only have one allele so only one recessive allele is required to produce recessive phenotype in males
49
Give example of characteristic that is determined by more than one allele
Blood groups are deternined by three alleles: IA, IB, IO,
50
What are the four different blood groups
A, B, AB, O
51
What are codominant alleles
Alleles that equally contribute to organism's phenotype. They are expressed to equal extent
52
Describe the codominance in blood groups
* IA and IB are codominant * IA IB gives blood group AB
53
Why does IA IO give blood group A
* IO is recessive to IA * IA is dominant and expressed giving blood group A
54
What are possible genotypes for blood group B
* IB IO * IB IB
55
What is genotype for blood group O
IO IO
56
What are two causes of variation that influence phenotype
* Genetic variation * Environmental variation
57
What is genetic variation
Different characteristics as a result of mutation and sexual reproduction
58
What is environmental variation
Different characteristics as a result of mutation and sexual reproduction
59
What is mutation
Random change to base sequence in DNA which results in genetic variants
60
What is Human Genome Project
* Scientific research project involving thousands of scientists across glove which successfully mapped entire human genome * Scientists now aim to identify function of every gene in human genome
61
How can results of Human Genome Project be applied to medicine
* Enables scientists to understand how lifestyle factors interact with genes - identifying predisposition to disease and possible preventions * Disease-causing alleles identified more rapidly and appropriate treatments prescribed earlier on * Scientists can predict individual's response to certain drugs. New drugs can be developed which are tailored to specific allele
62
How may a gene mutation affect an organism's phenotype
* Most genetic mutations have no effect on phenotype * Some mutations have small effect on phenotype * Rarely, a single mutation will significantly affect phenotype
63
Why is there usually extensive genetic variation within a population of a species
Because they arise through mutations

Biology (5 decks)

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