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Genetics Flashcards

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Biology 101 flashcards
1
Q

Genes

A

contain the information for protein synthesis, passed down from parents to offsprings
found on chromosomes

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2
Q

Alleles

A

different versions of the same genes, variations in traits are due to alleles

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3
Q

Genotype

A

based on the alleles inherited

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4
Q

Homozygous

A

2 copies of identical alleles

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5
Q

Heterozygous

A

2 different copies of an alleles

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6
Q

Dominant

A

ability to overshadow/mask
another allele it is paired with which will be considered as recessive.
Dominant traits are usually depicted with uppercase letters.

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7
Q

Phenotype

A

physical features portrayed based on the inherited genes, basically seen as the gene expression

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8
Q

Recessive

A

able to be masked and usually depicted with a lowercase letter

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9
Q

Diploid cells

A

contains 2 homologous copies of chromosomes, one from each parent, human diploid cells contain 46 chromosomes

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10
Q

Haploid

A

half the number of chromosomes found in diploid cells (23), these are usually seen in gametes (sperm and egg cell).
Haploids are formed via the process of meiosis.

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11
Q

Mendel’s laws of genetics

A

Experiments conducted on peas
Law of Dominance: between 2 different alleles, the dominant one usually masks the other.
Law of Segregation: chromosomes segregate into gametes in order to pass on genetic information.
Law of independent assortment: alleles on different chromosomes are randomly distributed into individual gametes.

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12
Q

Punnett squares

A

determines the possible outcomes of genetic crosses
establishes the probability of an offspring’s genotype

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13
Q

Zygosity

A

provides the degree of similarity between alleles which determines a specific trait, so a pair of alleles can be homozygous or heterozygous

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14
Q

Sickle cell Anaemia requires

A

offspring to inherit 2 copies of the recessive alleles

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15
Q

Sexual reproduction

A

complex process where 2 haploid gametes fuse to form a diploid cell.
A new individual is formed by the combination of sex cells from the parents thus producing a new combination of genes

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16
Q

Carriers

A

an individual who carries and is capable of passing on a mutation associated with a disease and they usually do not exhibit any symptoms

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17
Q

Sex-linked Genes

A

Genes found on the X chromosome but not on the Y chromosome are said to be X-linked and vice versa
genes have a unique pattern of inheritance due to both male and females possessing the X chromosome
much more X linked disorders than Y linked due to the X chromosome possessing >2x genes than the Y chromosome

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18
Q

X-inactivation

A

compensatory mechanism that reduces the dosage of gene products in females

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19
Q

Humans pairs of autosomes and pairs of allosomes

A

22 pairs of autosomes (non sex chromosomes)
1 pair of allosomes (sex chromosomes)

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20
Q

Allosomes that do not carry the same genes are considered

A

non-homologous in comparison to autosomes

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21
Q

x linked conditions

A

muscular dystrophy
colour blindness
haemophilia.

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22
Q

X recessive

A

females with one copy of the X-recessive mutation will be carriers, their symptoms if any is dependent on the notion of lyonization.
Males with the X-linked recessive condition will always have the condition as they possess only one copy of the gene, all of their daughters will be carriers and none of their sons will be affected assuming the mother does not have the mutation.
Carrier mothers have a 50% chance to pass the mutated gene assuming the father is without the mutation.
Examples of conditions with this pattern of inheritance are Haemophilia A and B, Colour blindness etc

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23
Q

X dominant

A

females with this mutation have a 50% chance of passing on the mutated gene to her offspring’s. If only the father is affected then 100% of his children will have the condition since they inherit their father X chromosome. Examples of conditions with this pattern of inheritance includes: Fragile X syndrome, Alport’s syndrome

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24
Q

Y-linked

A

occurs only in males, appears in all sons of males that possess the mutation.
Conditions associated with this pattern of inheritance include azoospermia and hairy ears.

25
Q

Crossing over

A

occurs in the germ line level where genes are swapped over, it increases genetic diversity

26
Q

Lyonization

A

X-inactivation which leads to the formation of a barr body, one of the X chromosomes in every cell in a female is randomly inactivated in early development.

27
Q

Skewed inactivation

A

preference to which X chromosome is inactivated in all cells

28
Q

Barr body

A

inactivated X chromosome

29
Q

Muscular dystrophy

A

muscles degenerate, affected boys are weak and immobile. Occurs due to mutated dystrophin protein which provides structural support to muscles allowing it to withstand the physical stress of contraction

30
Q

Colour blindness

A

mutation in the gene that encodes opsin, a visual pigment in the cone cells of the retina

31
Q

Haemophilia

A

2 forms of haemophilia are X-linked; haemophilia is bleeding disorders, haemophilia A is due to mutation of factor 8 whilst haemophilia B is due to mutation of factor 9. These factors play a vital role in the clotting and haemostasis.

32
Q

Azoospermia

A

cause of male infertility, there are no sperm cells in the semen produced

33
Q

Fragile X syndrome

A

learning disabilities, cognitive impairment and mental retardation due to mutation in the fragile X mental retardation 1 (FMR1) gene

34
Q

Alport’s syndrome

A

triad of eye problems, kidney and ear issues, and sufferers can have blood in the urine.
Mutation in a gene that encodes collagen.

35
Q

Mutations

A

alterations in the genetic material of a cell in a living organism
an occur in genes or chromosomes

36
Q

genetic mutations

A

changes in the nucleotides that make up the gene (point mutation)

37
Q

Chromosomal mutations

A

certain regions being translocated, deleted, duplicated, inserted and inverted
may arise from a virus, irradiation, and chemical assaults (mutagen)
errors during DNA replication, mitosis, meiosis which are left uncorrected
Chromosomal mutations usually occur during
mitosis or meiosis.
The abnormality may be numerical or structural.

38
Q

body can correct errors via

A

base excision repair mechanisms

39
Q

Polymorphisms

A

normal DNA variations that are common in the population

40
Q

Point Mutations

A

Usually occur during DNA replication or transcription where a nucleotide may be placed incorrectly, DNA and
RNA polymerase may make errors.
Also irradiation may increase the rate of errors.
In point mutations, a nucleotide or a few
of them may be placed inaccurately.
Point mutations occur via processes of substitution, insertion or deletion and may alter the protein sequence due to changes in the codon sequence.

41
Q

Silent mutation

A

the mutation still produces the same protein sequence

42
Q

Missense mutation

A

changes the codon
sequence thus a different amino acid presents.
For example sickle anaemia
where a point mutation swaps adenine for uracil (GAG to GUG) thus leading to swapping hydrophilic glutamic acid for hydrophobic valine

43
Q

Nonsense mutation

A

the codon sequence encodes a premature stop codon and this can lead to a non-functional protein

44
Q

Frameshift mutation

A

arises from a series of insertions or deletion thus resulting in shifting of the nucleobases which can encode an entirely different sand possibly non-functional protein.

45
Q

Numerical abnormalities (Aneuploidy) with chromosomes

A

result in loss or gains of chromosomes and it may also involve autosomes and allosomes.
arises from non-disjunction (failure to separate) during meiosis leading to monosomy, trisomy, and tetrasomy.
For example certain conditions arise from aneuploidy, Down syndrome (trisomy of
chromosome 21) and Turner’s Syndrome (loss of X (XO)) instead of XX)

46
Q

Structural abnormalities with chromosomes

A

Duplication
Inversion
Deletions
Insertion
Translocation
Ring chromosome
Mutagens

47
Q

Translocation

A

portion of a chromosome has been transferred to another chromosome that can be Reciprocal or Robertsonian.
These can lead to fused genes which produce fusion proteins.

48
Q

Ring chromosome

A

chromosome ends fuse together forming a ring, may arise due to radiation

49
Q

Mutagens

A

physical or chemical agents that alter genetic material (DNA) and thereby increase the frequency of mutations. Strong mutagens can induce chromosomal instability leading to chromosomal breakages and rearrangements

50
Q

physical mutagens

A

Ultraviolet radiation from the sun, ionising radiation (x-ray). Ultraviolet light (UVB) can promote the formation of pyrimidine dimers (thymine or cytosine).

51
Q

Chemical mutagens

A

alkylating agents (mustard gas), benzene, delaminating agents (nitrous acid), and reactive oxygen species (hydroxyl ions, hydrogen peroxide)
mustard gas
nitrous acid

52
Q

Base excision repair

A

process utilised to repair damaged DNA, removes helix distorting base pairs in a DNA molecule

53
Q

Nondisjunction

A

daughter cells have abnormal numbers of chromosomes due to their failure to separate during division

54
Q

Reciprocal translocation

A

balanced exchanges between homologous chromosomes, no genetic material is lost

55
Q

Robertsonian translocation

A

entire chromosome attaches to another via the centromere

56
Q

UV radiation

A

invisible rays of energy from the sun

57
Q

Ionizing radiation

A

particles and rays with sufficient energy and ability to ionize molecules

58
Q

Reactive oxygen species

A

unstable molecule that contains oxygen and easily reacts with molecules of a cell

59
Q

Turner syndrome

A

monosomy of X chromosome causing developmental problems, including short height, failure of the ovaries to develop and heart defects

cell bio (11 decks)

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