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Genetics Flashcards

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AP® Biology flashcards Biology 101 flashcards
0
Q

What are eukaryotic chromosomes made of?

A

DNA and proteins

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1
Q

What is a gene?

A

A veritable factor that controls a specific characteristic

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2
Q

What is an allele?

A

One specific form of a gene, differing from other alleles by one or a few bases and occupying the same gene locus as other alleles of the gene

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3
Q

What is a genome?

A

The whole of the genetic information of the organism

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4
Q

What is gene mutation?

A

A change to the base sequence of a gene

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5
Q

What is meiosis?

A

The reduction division of a diploid nucleus to form haploid nuclei

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6
Q

What are homologous chromosomes?

A

Chromosomes with the same genes as each other, in the same same sequence but do not necessarily have the same allele of those genes

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7
Q

What is the phenotype?

A

The expression of the gene

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8
Q

What is an autosome?

A

A body chromosome

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9
Q

What is the sex chromosome?

A

Chromosome 23 (XX female, XY male)

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10
Q

What is the gene locus?

A

The specific position of a gene on a locus

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11
Q

Compare mitosis and meiosis?

A

Mitosis : 1 division, 2 daughter cells, 46 chromosomes in daughter cell, function - produce replicate cells for growth and renewal

Meiosis : 2 divisions, 4 daughter cells, 23 chromosomes in daughter cell, produces gametes for reproduction

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12
Q

What is non-disjunction?

A

The chromosomes don’t come apart

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13
Q

What does non-disjunction lead to?

A

A gamete having an extra chromosome

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14
Q

What can a gamete having an extra chromosome lead to?

A 
Fertilisation of cell with the extra chromosome which leads to trisomy (three copies of chromosomes in a cell) 
Trisomy 21 (three copies of gene 21) leads to Down syndrome
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15
Q

What is karyotyping?

A

Where the feral cells are taken and the number of chromosomes are counted - check for disorders such as Down syndrome
Chromosomes are arranged in pairs according to their size and structure

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16
Q

Outline two ways cells can be retrieved for karyotyping?

A

Chorionic Villus Sampling (CVS) : take chorionic cells from chorionic villi from placenta by inserting a needle into the vagina

Amniocentesis : (5-10weeks) taking fluid from amniotic fluid. Use ultrasound to locate position of the fluid

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17
Q

How would you identify a foetus with Down syndrome from a karyotype?

A

Three chromosomes in chromosome point 21

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18
Q

How would you identify from a karyotype the gender of a foetus?

A

At 23rd pair:
Female has two X chromosomes
Male has one X and one Y (Y is smaller)

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19
Q

Define genotype

A

The alleles of a gene carried by an organism

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20
Q

What is the dominant allele?

A

An allele which is expressed whether homozygous or heterozygous

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21
Q

What is a recessive allele?

A

An allele which is expressed only when in a homozygous state

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22
Q

Define codominant alleles.

A

A pair of alleles which are both expressed when present

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23
Q

Define locus.

A

The particular position on homologous chromosomes of a gene

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24
Q

Define homozygous

A

Having two identical alleles of a gene

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25
Q

Define heterozygous

A

Having two different alleles of a gene

26
Q

Define carrier

A

An individual who is heterozygous for a recessive gene condition

27
Q

Define test cross

A

Testing a suspected heterozygous by crossing it with a known homozygous recessive

28
Q

What is an example of codominant and multiple alleles?

A

ABO blood groups

29
Q

How do the sex chromosomes control gender?

A

Females have two X chromosomes, males have XY
Y chromosome only has a few genes. Female always passes on X Male can pass on X or Y
If male passes on X = female; Y= male
Gender depends on sperm

30
Q

Define sex linkage

A

Alleles that are linked to sex disorders. Whose locus is on the X or Y chromosomes

31
Q

State two sex-linked disorders

A

Haemophilia

Colour blindness

32
Q

Why can a female be homozygous or heterozygous for sex-linked genes while males cannot?

A

Males can only be homozygous as they only have one X chromosome, whereas women have 2

33
Q

Why are sex linked disorders more common in males than females?

A

Females are carriers when they have dominant and recessive alleles together. Recessive alleles in a carrier does not affect the phenotype as dominant allele is also present. The gene is located on the X chromosome and not on the Y chromosome. Males only have one X chromosome and therefore only need one recessive allele to be a sufferer.

34
Q

How would you amplify and multiply minute quantities of DNA?

A

Polymerase Chain Reactions

35
Q

What is the role of Polymerase chain reactions?

A

To amplify and copy minute quantities of DNA

36
Q

What is gel electrolyisis?

A

An electric field and gel is used to separate fragments of DNA according to their size. Heavier fragments will stay closer to the origin whereas lighter fragments will migrate to positive end.
Restriction enzymes used to cut DNA into fragments. Gel supports. DNA but also lets some move through. Electric current draws DNA along the gel towards the positive anode. Fluorescent DNA markers allow you to see e bands of DNA.

37
Q

What process is used to separate DNA into its fragments for comparison with a sample of DNA?

A

Gel Electrophoresis

38
Q

What is gel electrophoresis used in?

A

DNA profiling

39
Q

Outline applications for DNA profiling

A

Determining family relationships
Criminal investigations to confirm suspects
Tracking individuals in a population
Rape cases

40
Q

How would DNA profiling be used to determine the guilt/innocence of a suspect in a murder investigation.

A

Sample of DNA is obtained
PCR is used to amplify the sample of DNA
DNA is broken into fragments by restriction enzymes
DNA fragments are separated by gel electrophoresis
DNA separated into a series of bands
Bands compared with different samples of DNA
If bands are the same, DNA is from the same source

41
Q

Why is it possible for a gene of one organism to be introduced and function in a different organism?

A

The genetic code is universal

42
Q

What are the advantages of producing Bt corn through gene transfer?

A

Allows for the introduction of a trait that wasn’t already in the gene pool
Results in an increased productivity of food production (same yield from less land)
Less chemical pesticides - reducing the cost of farming
Can now grow corn in areas that previously may not have been viable (less need for deforestation to help save the environment)

43
Q

Outline gene transfer.

A

Bacteria, such as E.coli has plasmids. These plasmids are cut by the restricted enzyme at specific points leaving sticky ends.
Other species’ DNA is cut by the same restriction enzyme to gain a desirable gene, such as a gene that produces insulin.
The DNA is added to plasmid. The DNA ligase will seal the plasmid, forming a recombient plasmid which are inserted into host cells. These host cells may be cloned and in the case of insulin, they begin to make insulin.

44
Q

What are the disadvantages of producing Bt corn through gene transfer?

A

Could have currently unknown harmful effects (allergic reactions) and could cause long term damage to the body as long term effects are not fully known
Accidental release of transgenic species may result in competition with or eradication of an existing plant species
Possibility of cross pollination (eg gene is introduced to weeds)
Reduces genetic variation/biodiversity (pests play a vital role in the ecosystem)

45
Q

Name two examples of the current uses of genetically modified crops or animals

A

The use of bacteria to produce GM bacteria which produces insulin which can be used for diabetes sufferers
The use of Bt crops which are resistant to pests

47
Q

Describe the consequence of base substitution mutation with regards to sickle cell anaemia.

A

Mutation leads to a change in DNA base sequence; changes mRNA during transcription; changes amino acid sequence; glutamic acid is changed to valine; changes shape of haemoglobin; becomes less soluble; cannot carry oxygen as well; sickle which impairs blood flow; causes anaemia, tiredness etc.

48
Q

Describe, with the aid of a diagram, the behaviour of chromosomes in the different phrases of meiosis.

A
  • chromosomes condense during prophase 1; homologous chromosomes pair up in prophase 1; crossing over in prophase 1.
  • movement of pairs of chromosomes to the equator in metaphase 1
  • movement of half of the chromosomes to each pole in anaphase 1
  • movement of chromatids to opposite poles in anaphase II
  • uncoiling in telophase II
49
Q

Outline one example of inheritance involving multiple alleles.

A

Multiple alleles means a gene has more than two alleles.
ABO blood groups are an example of multiple alleles, as it has three genes: IA, IB and i.
Any two of these alleles are present in any individual.
SHOW ALL SIX GENOTYPES WITH PHENOTYPES

50
Q

Outline sex linkage.

A

Most of the time sex-linked genes are carried on the X chromosome. Since females have two X chromosomes they have two copies of the sex-linked gene whereas males only have one since they only have one X chromosome. Women can only be chromosomes if only one X carrier is affected. Hemophilia and colour blindness are both examples of sex linkage.

51
Q

Outline three outcomes for sequencing the human genome.

A
  • International Cooperation
  • may lead to the production of gene probes to detect carriers of genetic diseases
  • study of similarities between human race
  • produce a complete gene map
52
Q

What happens to genes when they are transferred to another species?

A

The amino acid sequence of polypeptides translated remains unchanged because the genetic code is universal.

53
Q

Outline the use of restriction enzymes and DNA ligase in gene technology.

A

Bacteria (E. coli) has plasmids which are removed by enzymes at specific points, leaving sticky ends.
The other species DNA is cut by the same base sequence, which is then added to the plasmid at sticky ends.
The recombiant plasmid is inserted into new host cells which may be cloned.

54
Q

State two examples of the current uses of genetically modified crops or animals.

A

The transfer of a gene that gives resistance to the herbicide glyphosate from bacterium to crops so that the crop plants can be sprayed with the herbicide and not be affected by it.
The transfer of a gene for factor IX which is a blood clotting factor, from humans to sheep so that this factor is produced in the sheep’s milk, to treat haemophilia.

55
Q

Define clone.

A

a group of genetically identical organisms or a group of genetically identical cells derived from a single parent cell.

56
Q

Outline a technique for cloning using differentiated animal cells.

A

Dolly the sheep was cloned by taking udder cells from a donor sheep. These cells were than cultured in a low nutrient medium to make the genes switch off and become dormant. Then an unfertilized egg was taken from another sheep. The nucleus of this egg cell was removed by using a micropipette and then the egg cells were fused with the udder cells using a pulse of electricity. The fused cells developed like normal zygotes and became embryos. These embryos were then implanted into another sheep who’s role was to be the surrogate mother. One lamb was born successfully and called Dolly. Dolly was genetically identical to the sheep from which the udder cells were taken.

57
Q

What are the arguments for cloning?

A
  • Identical twins are formed by cloning so it is a natural process
  • cloned embryos can be tested for genetic disease
  • increased chance of children for infertile couples
  • cloning research may lead to spin-offs for other research areas, such as cancer/ transplant research
58
Q

What are the arguments against cloning?

A
  • reduces the value of individual psychological problems
  • high miscarriage rates
  • cloned individuals may show premature ageing
  • costly processes and money could be spent on other types of healthcare
  • may be done for inappropriate motives (to replace a lost loved one/perfect race etc.)
59
Q

In a pedigree chart, what shape represents males and what shape represents females?

A

Square represents males

Circle represents females

60
Q

Which of the following types of information are needed to construct a karyotype:
I: Size of chromosomes
II: Gene mutations of the chromosomes
III: Age of the individual

A

I: Size of chromosomes

61
Q

How does one carry out a test cross?

A

By crossing an allele with a homozygous recessive individual.

62
Q

Using a names example, discuss the benefits and harmful effects of genetic modification.

A

For example, wheat can be modified by Salmonella typhirium which gives resistance to roundup herbicide.

This allows the use of herbicides on growing crop, killing weeds but not the wheat. This allows for a higher yield due to less weed competition. This in turn protects the environment as less land needs to be cultivated to get the same yield.

However, the gene for herbicide resistance may be transmitted to weeds and uncontrollable superweeds might be produced which cannot be killed by herbicides. Also, the foreign DNA in the wheat may cause allergies in humans and have unknown health effects. Also the lack of weeds will alter the eco-system as wilFtsandlife will have less weeds to feed on.

63
Q

Describe with he aid of a diagram, the behaviours of chromosomes in the different phases of meiosis.

A

Prophase 1: chromosomes condense, homologous chromosomes pair up; crossing over occurs.
Metaphase 1: chromosome pairs move to the equator of the cell. Spindle microtubles extend from poles of the cell.
Anaphase 1: bivalvents are separated and moved to opposite poles of the cell.
Prophase 2: the cell has divided to form two haploid cells. Spindle microtubules extend again.
Anaphase 2: the chromotids separate move to opposite poles of the cell.
Telophase 2: chromosomes uncoil.

Biology (10 decks)

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