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Biology Lab > Genetics Lab (lecture) > Flashcards

Genetics Lab (lecture) Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is genetic variation?

A

genetic difference between individual within or different populations

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2
Q

What does variation cause?

A

different phenotypic characteristics (traits)

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3
Q

How can variation occur?

A

-On many scales- from gross alterations in human karyotype to a single nucleotide changes

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4
Q

What is a human karyotype?

A

an individuals collection of chromosome

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5
Q

what can variations be divided into?

A
  • Polymorphisms

- Disease causing mutation

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6
Q

What is a polymorphism?

A

If variations are found frequently in a population

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7
Q

What is a disease causing mutation?

A

detrimental in health

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8
Q

What IS variation?

A

driving force of evolution by natural selection therefore allowing us to adapt to other environments
-Genetic mutation is random hence some phenotypes could be either beneficial (over the others) or damaging to organisms.

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9
Q

What is an allele?

A
  • One or more gene given at a point (locus) on a chromosome.
  • Each allele in each person probably has a slightly different genetic code than the other one
  • May occur in pairs or multiple.
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10
Q

How can a mutation occur in a. allele?

A

at each locus point.

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11
Q

What are the different types of mutation?

A
  • Point mutations
  • Frameshift mutatations
  • Contiguous repeats ( repeat of 2 or 3 nucleotides)
  • CNV (Copy number variaiton)- genes multiplied or deleted
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12
Q

What is point mutation ?

A

.A point mutation is when a single base pair ( in a triplet/codon) is altered
which occurs by a simple mistake during DNA replication in meiosis
. sometimes such mutations can have severe consequences i.e.sickle cell anaemia

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13
Q

What is a frameshift mutation?

A

A frameshift mutation is a genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read.
. this is more serious

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14
Q

What happens when you assume a point mutation happens in an exon?

A

You can get:
1- Silent mutation- result in no change in amino acid sequence–> synonymous mutation
2. Missense- change in a sequence
3. Nonsense- premature stop codon

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15
Q

What is an exon?

A

expressed region of the genome

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16
Q

How can you Get a change in a nucleotide sequence but not an amino acid sequence?

A

Via the Silent mutation

  • As it may have created another codon which codes for the exact same amino acid
  • e.g. originally FOR Alanine (GCU) , and could have replaced ‘U’ with a ‘C’ so (GCC) however that codon codes still for Alanine.
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17
Q

What is a silent mutation?

A

a mutation in the nucleotide sequence which results in no change in the amino acid sequence.

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18
Q

What are the non synonymous mutations?

A
  • Missense

- Nonsense

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19
Q

What is a nonsense mutation?

A
  • Some nucleotide sequences (codon/triplet) don’t code for an amino acid however code for a signal to stop the process of translation.
  • occurs at end of a.a chain- protein made the sequence is coding for.
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20
Q

What is a missense mutation?

A
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21
Q

What does each a.a. acid have?

A

a specific characteristic to them

  • specific chemical propertires
  • e.g could have slightly positive, negative charge or neutral
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22
Q

What is a conservative missense mutation?

A

If the amino acid sequence is changed but retains biochemical properties- for e.g.- a.a is slightly changed, won’t have much effect on the folding of the a.a chain- however the protein made is able to perform the function of the original non-mutated protein or it may have no effect whatsoever?

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23
Q

What is a non-conservative missense mutation?

A
  • If the amino acid sequence is changed but changes biochemical properties
  • Massive effect of. how that a.a. chain folds into that protein - and so effects the function of the protein.
  • A signifcant effect on ultimate phenotype - could lead to a different trait or to a disease
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24
Q

What are insertions/deletions caused by?

A

-by frameshift mutation

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25
Q

What is the effect caused by insertions/deletion?

A
  • Changes how the following amino acids are read and coded for.
  • Altered reading frame
26
Q

What does the altered reading frame cause?

A

a frame shift mutation - when the insertion or deletion changes down stream reading of codons

27
Q

What happens if you have an insertion or deletion of 3 nucleotides long?

A
  • That is a non frame shift.

- Lead to either. complete deletion or inserion

28
Q

What are the polymorphisims?

A
  • Variants found in within more than 1% of the general population
  • More than 1 in 100 people share that genetic mutation
  • Found in such high prevalance within population, less likely to cause a genetic disease
  • Changes in genetic code for the disease won’t get passed on- less likely recurrence of reproduction
  • Selection pressure of people not mating with people of a genetic mutation.
  • Cause variation in phenotype
29
Q

What can polymorphisms affect?

A

-Disease predisposition,
progression, or drug response when combined with other genetic and environmental factors (disease risk factor)

-Good e.g when you get autoimmune disease -

30
Q

What are the 3 common types of polymorphisms?

A
  1. Single nucleotide polymorphism (SNPs)
  2. Small insertion/deletions (Indels)
  3. Large-scale copy number polymorphisms ( CNPs or CNVs)- whole changes in gene number
31
Q

What are SNPs?

A
  • is a point mutation
32
Q

How many nucleotides do we have in every nucleus?

A

6billion

-We differ one from another at approx 1:1000 nucleotides

33
Q

What is the percentage of human DNA being identical between individuals?

A

99.9%

34
Q

How much % do we differ of our genetic material?

A
  1. 1%
    - of the 0.1% - 80% of those differences are due to point mutations
    - Due to SNP - most common
35
Q

What are indels?

A
  • Insertions or deletions of nucleotide sequences of 2 -10,000 base pairs- can have large scale changes / regions
  • 2nd most common polymorphism
36
Q

How is polymorphism different from a mutation leading to a specific disease?

A
  • Purely the prevalence in the general population

- if the mutation is found in less than 1% of the population it is referred to as a MUTATION

37
Q

What are disease causing mutations?

A
  • if the mutations lead to a protein with loss of function or aberrant expression of a protein.
  • These disease causing mutations lead to different functioning protein after.
  • They are often in exons.
38
Q

What are the disease causing mutations referred to as?

A
  • Point mutations
  • frameshift mutations
  • inversions- flip around
  • copy number variations
39
Q

What are large changes in genetic material?

A

Chromosomal disorders

-Rare but significant phenotypical changes

40
Q

What happens in chromosomal disorders?

A
  • Complete loss or gain of chromosome- non-disjunction
  • Lead to rearrangement- Incorrect crossing over
  • loss of part of chromosome
41
Q

What are 3 regions of a chromosome?

A

-Centromere
-2 stretches of genetic material : P arm- short arm sticking out from centromere
And Q arm - long arm sticking out from centromere

42
Q

How is DNA coiled up into these region ?

A

Tightly packed (being dense) leads to puckering where centromere is.

43
Q

What happens when you stain the chromosomes?

A

-Banding patterns- diff bands and sub bands

44
Q

What happens when you uncoil a chromosome?

A
  • It is Tightly packed loops of DNA
  • its DNA wrapped around a nucleosome- which is formed from a protein called histone
  • -Un peel DNA strand from histone nucleosome- you see classic DNA double helix
45
Q

How many histone molecules do you have?

A

8 molecules- made up of 4 different types

Histone H2A, H2B, H3 , H4

46
Q

What are the histones?

A

-proteins that condense/coil and structure the DNA of eukaryotic cell nuclei into units called nucleosomes

47
Q

What is the histone octamer?

A

-Consists of 2 copies of each histone protein

48
Q

How is the nucleosome core formed?

A

-2 H2A-H2B dimers (bound together) and 1 H3-H4 tether (2H3 and 2H4)

49
Q

What is the nucleosome core structure?

A

8 histone molecules in the centre

-DNA chain coils around octamer time and is anchored by another histone molecule H1.

50
Q

How can we tell the gross structure of the chromosome?

A
  • Using a Karyogram- referred to as the Karyotype: look at structure and number of chromosomes, banding pattern of chromosome and count ,to check position of centromere to check for addition or deletion.
  • See sex chromosome- identify gender- any addition and deletion of chromosomes
51
Q

What is the process of a Karyogram?

A
  • Take cell sample
  • Culture in dish
  • Induce cell to go through mitosis
  • Arrest cell division during METAPHASE
  • Extract chromosomes from a single cell- during metaphase - once chromatins condensed down
  • Stain with Giemsa- to see the different density regions
  • Then align the autosome pairs up and put in chromosome order
  • Put in length order

Compare

  • Chromosome count
  • Centrosome position: length of P ARM and Q arm
  • Banding Pattern
  • Sex chromosomes
52
Q

What is the 1st chromosome rearrangements ?

A

-Balanced reciprocal Translocations- During normal process of Meiosis 1 you get a cross over- normal- deriving force of evoultion- allows for more possible genetic variations than mistakes in DNA copying (where DNA polymerase goes wrong

53
Q

What is the 2nd chromosome rearrangement ?

A
  • Centric fusion- Robertsonian
  • Chromosomes don’t line correctly within the tetrad- when crossing over occurs - may have Q arm of one chromosome being crossed over and replaced for the P arm of the other chromosome within that tetrad
  • End up with one chromosome with double amount of genetic material from Q arm to the P arm
  • Have 2 genes from every gene that would be found on just Q arm
  • Leads to massive change in genetic material- affect on phenotype of person
  • Essentially creating a person that has 3 copies of a lot of the genes- the phenotypes that come out of this will be similar to trisomy.
  • Lead to down syndrome phenotype- robersonian translocation of the Q arm on chromosome 21
54
Q

What is the 3rd chromomsal rearrangements?

A
  • Isochromosome- during separation of sister chromaitds- instead of having aplane of splitting down the middle off the chromosome- sometimes microtubules pull and split the sister chromatids incorrectly
  • Then when they separate one sister has 2 P arms and other sister has 2 Q arms
  • Leads to doubling up of the genetic material of the same of the chromosome
55
Q

What is the 4th chromosomal rearrangements?

A

Deletion/Insertion- when crossing over doesn’t occur properly and some fragments are lost rather than being inserted in other chromosomes
- Can occur during replication (interphase)- DNA polymerase may not have copied the genetic material or double up a large section of material

56
Q

What is the 5the chromosomal rearrangement?

A

Inversions- can have regions of alleles which are inverted within the chromosome.
This can either be around the centromere (pericentric)or within one of.the arms (paracentric)

57
Q

What is the 6th chromosomal rearrangement?

A

-Ring chromosome- genetic material fragmented off from end of chromosme- make molecule unstable- so stabilises itself by forming a ring

58
Q

What is subject to non-disjunction?

A

sex chromosomes

e. g females with only one X chromosome are suffering from turners syndrome
- the possession of XXX chromosomes is known as meta female syndrome
- XXY in males- kleinfelters syndrome

59
Q

What is downsyndrome?

A
  • Common chromosomal disorders
  • 1 in 800 people
  • 95% caused by trisomy of chromosome 21
  • Not all down syndrome caused by chromosome 21
  • 5% caused by Robertsonian mutation- 2 Q arms on one chromosomes - leads to phenotype of having trisomy chromosome
  • 40% develop cardiac problems
  • 10-20 increase risk leukaemia
  • more than 40 develop neuropathology
  • Autoimmune disease predisposition
  • Estropia and hyperopia
60
Q

explain chromosome structure ?

A
  1. at the simplest level , chromatin is a double - stranded helical structure of DNA
  2. DNA is complexed with histones to form nucleosome
  3. each nucleosome consists of eight histone proteins which wrap the DNA 1.65 times
  4. a chromosome consists of a nucleosome plus the H1 histone

Biology Lab (5 decks)

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