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Cellular Genetics & Cell Cycle > Genetics & Inheritance > Flashcards

Genetics & Inheritance Flashcards

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Biology 101 flashcards
1
Q

What is a MONOGENIC disorder?

Name an example.

A

A disorder associated with X1 Gene.

E.g. Cystic Fibrosis
Sickle-cell Anaemia

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2
Q

What is a POLYGENIC disorder?

Name an example.

A

A disorder associated with multiple genes.

E.g. Type-II Diabetes
Rheumatoid Arthritis

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3
Q

Genotypes can determine if you are resistant to a disease.

What gene affects an immunity from HIV-1.

A

CCR5 Chemokine Receptor (a protein on the surface of leukocytes). HIV uses these as a way of entering and infecting host cells.

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4
Q

Genes can determine responses to drugs.

Which enzyme is responsible for Codeine metabolism (& approx 25% of metabolism of all clinically used drugs)?

A

CYP2D6 - a member of the cytochrome P450 class of enzymes.

It converts Codeine into its active form (Morphine).

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5
Q

What is a gene?

A

A sequence of DNA nucleotides which encodes for a specific protein.

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6
Q

Explain the structure of chromosomes, beginning at the DNA level.

A

DNA - wrapped twice around X8 histone proteins = X1 nucleosome.

Multiple nucleosomes form chromatin.

When chromatin condenses chromosomes are formed.

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7
Q

What is a normal human karyotype?

A

46, XX (female)

or

46, XY (male)

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8
Q

How many pairs of autosomes does a normal person have?

A

X22

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9
Q

How many pairs of sex chromosomes does a normal person have?

A

X1

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10
Q

What is the implication of females having no Y chromosome?

A

That it contains no genetic information essential for the viability of humans.

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11
Q

What is the name given to the patterns of bands on chromosomes?

A

G-banding

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12
Q

Name the three locations the centromere can be found on sister chromatids.

A

Metacentric - two arms are almost equally (P-arm slightly smaller)

Submetacentric - shorter P-arm and longer Q-arm

Acrocentric- P-arm only exists as a satellite held on by a small stalk

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13
Q

Name the two arms of chromosomes.

A

P & Q arms.

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14
Q

What are the characteristics of MITOTIC daughter cells?

A

X2 daughter cells.

Each are diploid (X2 copies of each gene).

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15
Q

What are the characteristics of MEIOTIC daughter cells?

A

X4 daughter cells.

Each are haploid (X1 copy of each gene).

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16
Q

What is the name of the region on the Y chromosome that determines sex?

A

SRY Region - sex determining region.

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17
Q

What two genotype combinations can exist whereby the karyotype does NOT match the individuals gender?

A

XX Males (one X chromosome has the SRY region on its P-arm).

XY Females (Y chromosome is missing SRY region).

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18
Q

What percentage of spontaneous abortions are due to chromosome abnormalities?

And what percentage of these are due to trisomies?

A

50%

50% (therefore 25% overall)

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19
Q

What is the name given to a normal human karyotype with one EXTRA chromosome?

A

Trisomy.

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20
Q

What is the name given to a normal human karyotype with one LESS chromosome?

A

Monosomy.

21
Q

What is Aneuploidy?

A

A karyotype of chromosomes other than 46.

22
Q

What is Euploidy?

A

A karyotype of 46 chromosomes (full set).

23
Q

What is Trisomy 21?

46, XX or XY +21

A

Down Syndrome

24
Q

What are some of the clinical signs of Down syndrome?

A

Simians crease
Eyes lower than Earline
Wide nose bridge

25
Q

What is Trisomy 13?

46, XX or XY +13

A

Patau Syndrome

26
Q

What is Trisomy 18?

46, XX or XY +18

A

Edward’s Syndrome

27
Q

Which Syndrome does a karyotype of 47, XXY indicate and what are some of its symptoms?

A

Klinefelter Syndrome

Infertility
Small testes

28
Q

Which Syndrome does a karyotype of 47, X indicate and what are some of its symptoms?

A

Turner Syndrome

No growth spurt
Short in stature
Amenorrhoea (no menstrual cycle)

29
Q

What is the name of the only monosomy born?

A

Turner’s Syndrome

30
Q

What is the cause of aneuploidy?

A

Non-disjunction (failure of sister chromatids to separate during cell division) during oogenesis.

31
Q

What procedure on the amniotic fluid can test for chromosomal abnormalities?

A

Amniocentesis.

32
Q

Why does increases in age increase the risk of a trisomy?

A

Oogenesis is completed at birth and suspended in meiosis 1 therefore the ova are as old as the mother.

33
Q

What are the X5 modes of Mendelian inheritance?

A 
Autosomal recessive
Autosomal dominant
X-linked recessive
X-linked dominant
Mitochondrial
34
Q

Give an example or an autosomal recessive disease?

A

Cystic Fibrosis.

35
Q

What chromosome and gene are responsible for cystic fibrosis?

A

Chromosome 7

CFTR gene (Cystic fibrosis transmembrane conductance regulator)

36
Q

Give an example of an autosomal dominant disease?

A

Huntington’s disease

37
Q

Explain Huntington’s disease.

A

It is a mutation at the HD locus on chromosome 4 which causes an increase in the number of CAG repeats (glutamine) forming a longer than normal polyglutamine tract.

Normal <28 repeats
Abnormal >36 repeats which is a cytotoxic protein aggregation.

38
Q

What is cystic fibrosis?

A

Increased viscosity (thickness) of mucus due to a lack of expression of CFTR channels, which normally pump out Cl- which is followed by water. A lack of this makes the mucus more viscous leading to increased infections.

39
Q

What is genetic anticipation, as shown by conditions such as Huntington’s?

A

Whereby a condition becomes more severe or appears earlier in successive generations.

40
Q

Why do heterozygous individuals suffering with Huntington’s still get the disease.

A

Even if the wild-type allele will not produce excessive CAG repeats, the one mutant copy of the allele will which is enough to cause them to aggregate.

41
Q

What is meant by the term progeny?

A

Offspring.

42
Q

What is meant by diploid?

A

Each cell has X1 copy of each gene.

43
Q

What is meant by haploid?

A

Each cell has X2 copies of each gene.

44
Q

Give an example of an X-linked recessive disease.

A

Haemophilia A

Duchenne muscular dystrophy

45
Q

What is affected in haemophilia A?

A

A mutated gene for clotting factor VIII (8)

46
Q

Give an example of an X-linked dominant disease.

A

Vitamin D resistant rickets

47
Q

What are the two types of twins?

A

Monozygotic (X1 sperm / X1 egg)

Dizygotic (X2 individual conceptions)

48
Q

What is meant by twin concordance?

A

The extent to which twins possess the same same trait.

Higher concordance in monozygotic twins indicated genetics plays a larger role in that condition.

Cellular Genetics & Cell Cycle (8 decks)

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