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Genes and Inheritance Flashcards

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1
Q

what does DNA carry and what are their regions called and what does this determine?

A

DNA carries hereditary information and instructions.

They have regions called genes which contain information on what you look like.

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2
Q

what are nucleotides?

A

the building blocks of DNA

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3
Q

what are nucleotides made up of? where are these located?

A

Composed of phosphate, sugar deoxyribose and one base (adenine, cytosine, guanine or thymine).
Sugars are five-carbon and called deoxyribose. Carbons are numbered 1’-5’.
Phosphate at 5’.
Base at 1’.
Purines (double ring): adenine and guanine.
Pyridines (single ring): thymine and cytosine.

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4
Q

how are nucleotides connected?

A

Nucleotides are connected by covalent phosphodiester bonds between a 5’ carbon and a 3’ carbon on the other.
Polynucleotide chains run from 5’ to 3’.

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5
Q

how is a DNA molecule made up? how is it held together? what are the bases? how does this form a helix?

A

DNA molecule is made up of two polynucleotide chains.
Held together by hydrogen bonds between complementary bases.
A and T.
G and C.
For bases to face each other, one must be antiparallel (run 3’ to 5’ rather than 5’ to 3’).
The twist to form a helix.

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6
Q

what is the genome? how big is the human one?

A

Total of an organism’s DNA measured in the number of pairs contained in a haploid set.
Because sets of chromosomes are almost identical.
50 million to 300 million base pairs on a chromosome.
Human genome is 3234 million base pairs.

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7
Q

what is a gene? what do they do? what determines what a gene will control for?

A

Gene is a unique sequence of DNA.
Carry instructions for cells.
A unit of heredity, made up of a unique sequence of DNA that determines characteristics.
Nearly all genes code for proteins.
The length of the DNA and the order of base pairs determines what genes will control for.

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8
Q

what are alleles? how are they in somatic cells?

A

Different forms of genes that determine traits.
Somatic cells of a diploid organism contain two alleles for every gene, with one allele for every gene in a organism inherited from each parent.

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9
Q

what was the human genome project?

A

Human genome project was the biggest biological project ever.
It sequenced a human genome.
Started in 1990, ended in 2003.
Determined the order of nucleotides and the number of genes in an individual.

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10
Q

what is the role of genomic research?

A

sequencing genes of many organisms, comparing relatedness between species, determining gene function, early detection and diagnosis of human diseases

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11
Q

how is sequencing genes of many organisms useful?

A

Used it to understand the function of important genes in agriculture.

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12
Q

how is comparing relatedness between species done? how is it useful?

A

DNA sequence of a gene determines the amino acid sequence for proteins.
Comparing proteins can show the relatedness, especially in functioning between organisms.
Evolutionary traits can be seen using phylogenetic trees.
Number of differences in sequences shows how long ago they diverged.
Can track parthogenic organisms using sequenced.
Influenza can be traced in strains.
RNA could be sequenced to determine that various strains evolution.
Evolution can help predict what stains may arise and find treatments for them.
Comparing DNA can determine which organisms will be suitable to reflect human reactions is certain tests.

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13
Q

how is determining gene function done or useful?

A

Protein encoded by a gene must be identified in order to study its location and function.
Gene sequence can be compared to other species for which their gene function is known.
Genes can be modified and then inserted and once determining what the modification does, the normal function can be determined.
Genes can be disabled.

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14
Q

how is early detection and diagnosis of human diseases useful or done?

A

Can identify base differences in a gene suspected to be the cause of a disorder.
Compare those genes to healthy genes.
A person with family history can determine if they carry the gene and can then take preventative measures.

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15
Q

what is a chromosome?

A

Chromosome: a structure containing a single DNA molecule associated with proteins.

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16
Q

how do eukaryotic chromosomes differ to prokaryotic ones?

A

Eukaryotes have linear chromosomes.

Prokaryotes have a single circular chromosome and have smaller DNA molecules called plasmids which move between cells.

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17
Q

what is the structure of a chromsome?

A

DNA is coiled around proteins called histones forming a nucleosome.
Looks like a string of beads.
Packages efficiently and protects from enzyme degradation.
To condense, nucleosomes fold producing supercoils.

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18
Q

what are the types of chromosomes?

A

Centromere divides chromosome into two arms- short is p arm and long is q arm.
Types are based on position of the centromere:
metacentric (centred).
Submetacentric (long twice as long as short)
Acrocentric (very close to end)
Telocentric (at the end)

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19
Q

how does size of chromosomes differ?

A

Size differs by amount of genes and spacer DNA.

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20
Q

what are loci?

A

Genes are on particular regions called loci.

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21
Q

how are genes separated?

A

Genes are separated by spacer DNA- DNA which does not code for proteins and allows enzymes etc. to interact with genes easily.

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22
Q

what is policy level and what does this determine?

A

Number of sets is called policy level.

Number determines the characteristics of organisms.

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23
Q

what is a homologous chromosome? what about male sex chfomrmses?

A

Homologous chromosomes: same genes are found at the same loci.
Male sex chromosomes are not homologous but act like it during division.

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24
Q

what are sex chromosomes? what is homogametic and heterogametic?

A

allosomes.
Involved in sex determination.
X and Y.
Homogametic: two similar sex chromosomes.
Heterogametic: different sex chromosomes.
All eggs have an X.
50% of sperm have an X and 50% have a Y.

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25
Q

what are karyotypes? why are they stained? how are they arranged?

A

Study chromosomes at metaphase when they are most visible.
Stained so bands can be seen.
Karyotype: image or picture of a full set of chromosomes from a cell.
Arranged in pairs based on length, centromere and bands.

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26
Q

describe the human karyotype?

A

Autosomes are numbered 1-22.
Ordered in height.
Determine sex.

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27
Q

what is aneuploidy? monosomy? trisomy?

A

Aneuploidy is an abnormal number of chromosomes.
Monosomy one is missing.
trisomy an extra one.

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28
Q

Down syndrome, kleinefelter syndrome, pat syndrome and Turner syndrome?

A

down syndrome: extra 21- intellectual disability, may be infertile.
Klinefelter syndrome: extra X (XXY)- male, sterile, intellectual disability, female secondary sex traits (larger breasts).
Patau syndrome: three chromosome 13- small skull, intellectual disability, cleft lip, cleft palate, heart defects, seldom survive long past birth.
Turner syndrome: all or part of an X missing- female, short, infertile, fluid retention, puffy hands and feet, kidney and heart problems, some learning difficulties but most have normal intelligence.

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29
Q

what is a genotype? dominant, recessive, homozygous, heterozygous?

A 
set of alleles present in the DNA of an individual.
Dominant: A
Recessive: a
homozygous: AA or aa
Heterozygous: Aa
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30
Q

what is a phenotype?

A

observable characteristics it is a result go inheritance and the effects of the organisms environment.

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31
Q

are genes dominant or recessive?

A

Genes are not dominant or recessive but alleles are.

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32
Q

what is complete dominance?

A

Aa is not a mix but displays the dominant A.

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33
Q

what is co-dominace?

A

Red flower and white flower produce pink flower.

34
Q

what is polygenetic inheritance?

A

More than one gene contributes to the phenotype.

35
Q

describe height and human skin colour

A

Height in humans
Height is controlled about 50 genes or regions of the genome.
Genes that control for hormones etc.

Human skin colour
Determined by amount of melatonin (dark pigment).
At least four genes are involved in melatonin production.

36
Q

what are other influences o phenotype?

A

amino acids, cold, pH, epigenetics

37
Q

what is phenylketonuria?

A

PKU
Build up of amino acid in the blood.
Affects nervous system and intellectual ability.
Modify diet (environment) to have less phenylalanine.

38
Q

what is fur colour in Himalayan rabbits?

A

Cold causes black fur.

39
Q

what is flower colour in hydrangeas?

A

pH changes colour.
Acidic blue.
Alkaline pink.

40
Q

what are epigenetics?

A

Interaction of DNA with other molecules.
A tag of a molecule is added which changes gene expression.
During formation of gametes, tags are usually erased (reprogramming).
Some evidence that some epigenetic changes are inherited.
May explain why one indexical twin gets a genetic disease and the other does not.

41
Q

in a homozygous cross, what is the parental generation?

A

WW x ww
W red
w white

42
Q

what is the F1 generation?

A

All are Ww

If all are red, then W is dominant.

43
Q

what is the F2 generation?

A

Ww x Ww
Produces WW, Ww, ww
1:2:1 in genotype
3:1 or dominant:recessive

44
Q

what is the law of segregation?

A

Each daughter cell receives one chromosome from each homologous pair in meiosis.
The alleles for each trait are separated into different gametes.
Offspring will receive one allele from each parent at fertilisation.

45
Q

what does a test cross determine? how is it done?

A

Whether or not individual with dominant phenotype is AA or Aa.
Cross with homozygous recessive.
If all offspring have the dominant phenotype, the parent is homozygous.

46
Q

what is autosomal co-dominance?

A

Blending of phenotypes.

Use subscripts because neither allele is dominant.

47
Q

describe ABO blood grouping? what are the recessive and dominant ones, what are the phenotypes?

A

Human blood type is an example of autosomal co-dominance.
A and B are co-dominant and O is recessive.
Possible ones: A, B, AB or O phenotypes.

48
Q

describe ABO blood grouping in terms of multiple alleles at a single locus?

A

Blood has multiple alleles at the same locus.
I^A codes for A antigen.
I^B codes for B antigen.
i does not produce either and is recessive (ii is O).

49
Q

what is sex-linked inheritance?

A

Genes inherited off sex chromosomes.
Carry genes other than sex determination.
Females are homogametic (XX).
Males are heterogametic (XY).

50
Q

what is X-linked recessive inheritance?

A

Males usually only show recessive because they have one X.

Ratios of males and females are different.

51
Q

what is x-linked dominant inheritance?

A

Father is affected, all females children will be affected.

52
Q

what is y-linked inheritance?

A

Has few genes.

Never seen in females

53
Q

what is sex-limited inheritance?

A

Only affects one sex because the feature effected is only seen in that sex.

54
Q

circles, squares, horizontal line, vertical line, roman numerals, dot?

A

Circles are females
Squares are males
Horizontal line is a cross
Vertical line is offspring
Generations are represented with roman numerals
A carrier of an X-linked trait is shown with a dot in the symbol

55
Q

when is autosomal recessive inheritance likely?

A

Likely when parents do not have the trait but some children do.
Trait often skips generations.

56
Q

when is autosomal dominant inheritance likely?

A

Likely if both parents show the trait but some offspring do not.
May be seen in all generations.
Individuals that have it must have at least one parent who has it.

57
Q

how can autosomal and sex-linked inheritance be distinguished?

A

Can involve males having it more.

Frequency of it across generations.

58
Q

when is x-linked recessive inheritance likely?

A

Usually affect more males than females because males inherit one X, while females inherit two.
Females must have two recessive alleles for it to show.

59
Q

when is x-linked dominant inheritance likely?

A

Rare
Affect more females than males because females inherit two X’s and are twice as likely as males to get a dominant one.
Affected males have affected daughters and sons who are not.

60
Q

when is y-linked inheritance likely?

A

Any traits carried on a Y will be passed down to sons but not daughters.
Only males are affected.
All male offspring are affected.
The trait is observed in every generation with males.

61
Q

how can sex-linked inheritance be ruled out?

A

If an affected mother does not have an affected son, X-linked recessive can be ruled out.
X-linked dominance must involve affected fathers, giving the trait to all daughters.
Y-linked must have no females.

62
Q

what are the steps for determining it it is sex linked or autosomal?

A

Is it sex-linked?
Are mostly males affected? If only males are affected, and the trait passes from father to son in every generation, it os Y-linked.
Do affected daughters have affected fathers?
Do affected mothers have affected sons but not affected daughters? 2 and 3 suggest X-linked recessive.
If the answers are all no, it is autosomal.

Is it autosomal?
Look for two affected/unaffected parents that have differing children.
If two unaffected parents have affected offspring, it is autosomal recessive.
If two affected parents have an unaffected offspring, it is autosomal dominant.

63
Q

what is independent assortment

A

Alleles of a gene controlling a trait sort independently of alleles of another gene controlling a different trait.

64
Q

in independent assortment what is the F1 generation?

A

One homozygous dominant and the other homozygous recessive.

25% of any allele showing

65
Q

in independent assortment, what is the F2 generation?

A

Heterozygotes from F1 can be crossed (dihybrid cross) to produce F2.
Ratio of phenotypes: 9:3:3:1

66
Q

what is the dihybrid summary for independent assortment? and when is the 9:3:3:1 ratio observed?

A 
9:3:3:1 is observed in the F2 of a dihybrid heterozygous cross if:
The two genes control different traits.
There are alleles for each gene.
One phenotype is dominant.
Both are autosomes.
The two genes assort independently.
67
Q

what is linkage?

A

Linkage: tenancy for two or more genes located on the same chromosome to be inherited together.
The closer the genes, the more likely to link.
Linkage is never complete because of crossing over in meiosis.

68
Q

what happens to the ratio with linked genes?

A

When genes located on the same chromosome are inherited together, the ratio is 3:1.
Because they are inherited together, there is no crossing over so only two gametes (AB and ab) are formed.

69
Q

what is crossing over?

A

exchange of chromosomal material between members of a homologous pair of chromosomes during meiosis.

70
Q

what are the two outcomes of recombination?

A

Outcome 1 of recombination: crossing over does not occur between A and B loci. Only AB and ab combinations are made which are parental as they gametes AA, BB, aa and bb were produced.
Outcome 2: crossing over occurs between A and B. combinations AB, Ab, aB and ab are made. Some are parental (AB and ab) but some are recombinant (Ab and aB).

71
Q

what are recombinant gametes? what determines the likely hood of recombinants and how does this link to linkage?

A

carry a combination of alleles not observed in the parents.
The closer the genes, the less likely cross over is to occur, the more rare recombinants and the more common parental.
If genes areas far apart that 50% of gametes are recombinants, then independent assortment has occurred.
Less than 50%, genes are linked.

72
Q

what us genetic testing?

A

Medical test that detects specific alleles, mutations, genotypes or karyotypes associated with traits.
Used to determine ancestry and used in forensics.

73
Q

what is molecular genetic testing?

A

Used to find single genes or short lengths of DNA.
Mutations etc. can be found.
Useful for determining the function of proteins.

74
Q

polymerase chain reaction (MGT)

A 
DNA amplification (makes many copies) of a piece of DNA. 
Amplified DNA is then sequenced to find mutations etc.
75
Q

restriction fragment analysis (MGT)

A

DNA fragments are made by cutting DNA with restriction enzyme digestion.
Fragments are separated using gel electrophoresis.
Used to identify alleles.

76
Q

comparing DNA by Gell electrophoresis (MGT)

A

DNA molecules are separated into a slab of jelly-like substance called agarose.
Can compare DNA between individuals.
Banding patterns are seen.

77
Q

cytogenetic testing (MGT)

A

Two types:

Conventional cytogenetic testing karyotyping
Detects numerical or structural problems with chromosomes at metaphase.

Molecular cytogenetic testing by FISH
Fluorescently labelled nucleic acid DNA fragments are allowed to hybridise or attach to whole chromosomes.
Chromosomes are then assessed for changes such as duplications.

78
Q

biochemical genetic testing (MGT)

A

Detects levels of proteins.
Abnormalities suggest changes to DNA.
Used when specific defect has not been identified and it could be a number of genes.

79
Q

what are applications of gene testing technologies?

A

Intervene in evolution.
Genetic screening for diseases.
DNA profiling for criminals etc.

80
Q

describe the advantages and disadvantages of reproductive technology for screening embryos

A

IVF improves chances of having children but affects evolution.
Knowing the chances of disease, people may abort.
Can increase chances of a foetus surviving.
Genetic screening can happen before implantation.
Can choose to avoid having children with disorders.
Parents can prepare.
Treatment can start early.
Abortions increase.
Depression for child who knows they will develop a disorder.

81
Q

what are limitations of genetic testing?

A

Do not identify all mutations.
Limited predictive value.
Difficult decisions without full information.
Cannot determine how severe a disorder will be.

82
Q

other social and ethical issues with genetic testing (6)

A

There is treatment for some but not all conditions
Why bother knowing?

Availability of treatments
Should people be screened for something for which there are no treatments?

Genetic testing for some conditions is not diagnostic
May just say that you have a higher chance.
May lead to irreversible decisions.

Privacy issues
Whether or not DNA information should be told to families is controversial.
Discrimination for insurance people.

Embryonic stem cells and ethical issues
Destruction of embryos

Gene therapy and ethical issues
Can insert a healthy gene into someone who has an affected gene.
Will this endanger?

Biology (16 decks)

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