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Biology Mrs Champion > Genetics > Flashcards

Genetics Flashcards

1
Q

What is a DNA polynucleotide?

A
  • Many nucleotides bonded together in a long chain
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2
Q

What are DNA molecules made up from?

A
  • 2 polynucleotide strands with alternating deoxyribose sugars and phosphate groups bonded = sugar-phosphate backbone
  • Running in anti-parallel
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3
Q

What are the bonds called between the sugar-phosphate backbone?

A
  • Phosphodiester bond
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4
Q

What bonds are between the 2 anti parallel DNA polynucleotide strands?

A
  • Hydrogen bonds
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5
Q

What bases pair with which?

A
  • Adenine pairs with thymine
  • Guanine pairs with cytosine
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6
Q

What is a mutation?

A
  • A change in the sequence of bases in the DNA
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7
Q

How do mutations occur? How is the rate increased?

A
  • Randomly
  • Rate is increased by mutagens
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8
Q

What is a beneficial effect of mutations?

A
  • They gain phenotype advantage
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9
Q

What is the damaging effect of mutations?

A
  • They can be fatal and or a disease causing phenotypic changes
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10
Q

What are the 3 main ways that a mutation in the DNA base sequence can occur?

A
  • Insertion
  • Deletion
  • Substitution
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11
Q

Explain insertion

A
  • Changes the amino acid that would have been coded for by the original base triplet. It creates a new, different triplet of bases
  • Has a knock-on effect by changing the triplets further in the sequence
  • Might dramatically change the amino acid sequence produced
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12
Q

Explain deletion

A
  • Changes the amino acid that would have been coded for
  • Has a knock-on effect by changing the groups of 3 bases further in the sequence
  • May dramatically change the amino acid sequence produced
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13
Q

Explain substitution of nucleotides

A
  • Will only change the amino acid for the triplet in which the mutation occurs
  • Wont have a knock on effect
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14
Q

What is a structural gene?

A
  • Codes for protein that has a function within the cell
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15
Q

What are regulatory genes?

A
  • Codes for proteins that control the expression of structural genes
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16
Q

What does the lac operan do as controlling genes?

A
  • Controls the production of lactase
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17
Q

What is the structure of the lac operon?

A
  • Promoter = length of DNA onto which RNA polymerase binds for transcription of structural gene
  • Operator = length of the DNA that can switch structural genes on and off
  • structural gene = codes for the enzymes lactase, transaetylcase
  • regulator gene - codes for repressor protein which prevents the transcription of structural genes
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18
Q

What happens which there is no lactose present?

A

1) Regulatory gene is expressed so repressor protein is synthesised
2) Repressor protein blocks promotor protein region by binding to operator region
3) RNA polymerase cannot attach to promotor region, so no mRNA can be made from structural genes
4) No mRNA means no translation of structural genes into lactose-related enzymes

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19
Q

What happens when there is lactose present?

A

1) Regulator gene is expressed and repressor protein is produced but lactose binds to this and causes a conformational shape change (it cant bind to operator region)
2) Promoter region is clear so RNA polymerase binds and controls mRNA transcription of structural genes
3) Lactose-related genes are transcribed and translated so that E.coli can now use the available lactose

20
Q

What does CAMP repressor protein do to overcome the slow rate of structural gene transcription?

A
  • It binds to the operon
  • Occurs when CRP and cAMP are already bound
21
Q

What happens to cAMP levels when glucose is present?

A
  • They reduce
22
Q

What are homebox genes?

A
  • Contain a homebox with 180 base pairs coding for part of a specific protein
  • Found in hox clusters
23
Q

Do animals have similar of dissimilar hox genes?

A
  • Similar
24
Q

What are embryonic segments called?

A
  • Somites
25
Q

What is a hox gene?

A
  • Controls where body parts are positioned
26
Q

What are 2 categories of body plans and how many tissue layers do they have?

A
  • Diploblastic has 2 tissue layers (coral, jellyfish)
  • Triploblastic has 3 tissue layers (animals)
27
Q

What is apoptosis?

A
  • Added detail to animals
  • Programmed cell death that occurs in multicellular organisms (for example, fingers in humans)
28
Q

What factors affect hox gene expression?

A
  • Hormones
  • Drugs
  • Tempurature
  • Light intensity
  • Psychological
29
Q

Where does genetic variation come from?

A

The combination of alleles you inherit

30
Q

What is codominance?

A
  • Occurs when 2 alleles of a gene are equally dominant. If both present, they are both expressed in the phenotype
31
Q

What is linkage?

A
  • When 2 or more genes are located on the same chromosome and are therefore naturally inherited together
32
Q

What is dihybrid inheritance?

A
  • The inheritance of 2 different genes coding for 2 different characteristics
33
Q

What is evolution?

A

The change in inherited characteristics of a group of organisms over time

34
Q

What is sexual selection?

A

Characteristics that maximises an individuals ability to reproduce successfully so can be highly adaptive and sexually selected

35
Q

What is genetic drift?

A
  • Random changes of the number of gene variants in a small population
36
Q

What is a mutation?

A
  • A change in DNA sequence
37
Q

What is natural selection?

A
  • The ability to survive in a particular environment which impacts on genes or traits
38
Q

What is gene flow?

A
  • Movement of genes in and out
39
Q

What does a large population have?

A
  • A large gene pool which leads to lots of variation
40
Q

What are the 3 types of selection and explain

A
  1. Disruptive = selection pressures work towards the extremes and creates 2 modal values
  2. Stabilising = selection pressures works towards the centre increases the number of individuals at the modal value
  3. Directional = selection pressures work towards one extreme and moves the mode in this direction
41
Q

What does HW predict

A
  • the frequencies of particular alleles occurring in a population
42
Q

How does the frequency of allles in a gene remain constant ?

A
  • Large popualtion
  • No immigration or emigration
  • Random mating
  • There is no gene mutation
43
Q

What is speciation?

A

— The formation of a new species through evolution
- The new species is unable to reproduce to create fertile offspring with members of original species

44
Q

What 3 events leads to speciation?

A
  1. Members of a population become isolated
  2. Alleles within the populations undergo mutations randomly
  3. Mutations accumulate
45
Q

What is allopatric speciation?

A
  • Where members of a species are geographically isolated by a physical barrier

Biology Mrs Champion (5 decks)

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