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Bioscience > Genetics > Flashcards

Genetics Flashcards

1
Q

Define inheritance

A

Passing of hereditary traits from one generation to the next

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2
Q

What is the difference between genotype and phenotype?

A 
Genotype 
The genetic makeup of an organism
Can be determined by observing DNA
Completely depends on gene sequences 
Inherited by offspring

Phenotype
Visual properties and behaviours of the organism
Determined by observing outward characteristics
Depends on genotype and environmental factors
Not inherited by offspring

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3
Q

What are homologous chromosomes?

A

Homologous chromosomes are the chromosomes which contain alleles for the same type of genes (both look the same)

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4
Q

What are non-homologous chromosomes?

A

Non-Homologous chromosomes are chromosomes that contain alleles for different type of genes

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5
Q

What is an allele?

A

A different form of the same gene

BB dominant
bb recessive

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6
Q

What is homozygous?

A

A person with the same alleles on both chromosomes

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7
Q

What is heterozygous?

A

Having different alleles on homologous chromosomes

Heterozygous individuals are carriers of a recessive gene

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8
Q

What type of genotype leads to PKU?

A

Homozygous recessive

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9
Q

What is the term for fraternal twins and how are they formed?

A

Dizygotic

The independent release of 2 oocytes (cells in the ovary) fertilized by 2 separate sperm

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10
Q

What is the term for identical twins and how are they formed?

A

Monozygotic

2 individuals that develop from a single fertilized ovum
genetically identical & always the same sex

If ovum does not completely separate, conjoined twins (share body structures)

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11
Q

Name the 4 types of bases that make up a strand of DNA

A

Tymine (T)

Adenine (A)

Guanine (G)

Cytosine (C)

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12
Q

How many chromosomes do human body cells contain?

A

46 chromosomes

23 pairs

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13
Q

What are chromosomes made of?

A

DNA

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14
Q

What is the term/name of chromosomes 1-22?

A

Autosomes

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15
Q

What is the 23rd pair of chromosomes called?

A

Sex chromosomes

XX = Female
XY = Male
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16
Q

What is a karyotype?

A

A pattern of either a male or female chromosomes

46, XY = Male
46, XX = Female

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17
Q

What chromosomes is the gene for cystic fibrosis located?

A

Chromosome 7

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18
Q

What chromosomes is the gene for sickle cell disease located?

A

Chromosome 11

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19
Q

What type of order are genes arranged in on a chromosome?

A

Linear

20
Q

Define nondisjunction

A

Chromosomes fail to separate properly

Cell with one or more extra or missing chromosomes is called an aneuploid
(2n-1) is missing a chromosome
(2n+1) has an extra chromosome

21
Q

Define aneuploid

A

Cell with one or more extra or missing chromosomes

22
Q

Define translocation

A

Location of chromosome segment is moved

Crossing-over between 2 nonhomologous chromosomes

Down syndrome results from a portion of chromosome 21 becoming part of another chromosome

Individuals have 3 copies of that part of chromosome 21

23
Q

3 most common autosome anomalies

A

Down syndrome (trisomy 21: 47,XX,+21)

Edwards syndrome (trisomy 18: 47,XX,+18)

Patau syndrome (trisomy 13: 47,XX+13)

24
Q

2 most common sex chromosome anomalies

A

Turner syndrome 45,X

Klinefelter syndrome 47,XXY

25
Q

What causes down syndrome?

A

Nondisjunction of chromosome 21 (trisomy 21)

More common in older mothers due to more exposure to radiation & chromosome-damaging chemicals

1 in 800 infants is born with Down syndrome
mental retardation, distinctive facial structures & malformation of the heart, ears, hands & feet

26
Q

Define mutation

A

An alteration or change in the genetic material

27
Q

Causes of a mutation

A

Inherited

Exposure to mutagenic agents

Spontaneously through errors in DNA replication/repair

28
Q

What is amniocentesis? Describe the process? At how many weeks?

A

Pre-natal diagnosis to detect chromosome abnormalities

Take 10-20 ml amniotic fluid at 15-17 weeks gestation

A syringe inserted through the abdomen under ultrasound guidance

Foetal cells cultured for chromosome analysis

Risk of miscarriage about 0.5%; small risk of infection

If termination- labour is induced

29
Q

Why would someone get a prenatal diagnosis?

A

Avoid birth of affected baby eg with Down Syndrome

Know in advance & prepare for birth/treatment

Relieve uncertainty

30
Q

Define genes

A

Genes are codes for cells to make proteins

Genes are located on chromosomes

31
Q

The term for alterations in single genes

A

Single gene disorder

32
Q

The term for variants in genes

A

Multifactorial disease (+environment)

33
Q

Chromosomal imbalance term

A

Chromosome disorder

34
Q

What are the 3 types of single gene disorders?

A

Autosomal dominant - always expresses itself

Autosomal recessive - only expresses in the absence of dominant unaltered gene – healthy carrier

X-linked - genes found on X chromosomes

35
Q

Define autosomal dominant, recissive and x-linked recissive

A

Dominant
These individuals are called Heterozygotes with one copy of the altered gene they are affected

Recessive
Homozygotes must have two copies of the altered gene to be affected

X-linked recessive
Males with an altered gene on the X-chromosome are always affected

36
Q

Name 3 audtosomal dominant conditions

A

Huntington disease

Neurofibromatosis type 1

Marfan syndrome

Familial hypercholesterolemia

Familial Adenomatous Polyposis (FAP)

Prader-willi

37
Q

Name 3 autosomal recissive conditions

A

Sickle Cell disease

Cystic fibrosis

Batten Disease

Congenital deafness

Phenylketonuria (PKU)

Spinal muscular atrophy

Recessive blindness

Maple syrup urine disease

38
Q

Signs of Marfan syndrome

A

Tall stature
Elongated thin limbs and fingers
High risk of heart defects
Disloacted lens

39
Q

Signs of sickle disease

A

Abnormal haemoglobin

Bony infarcations in the phalanges and metacarpals can result in unequal finger length

40
Q

Name 3 x-linked recissive conditions

A

Fragile X syndrome

Haemophilia

Duchenne muscular dystrophy (DMD) (Becker BMD)

Fabry disease

Retinitis pigmentosa

Alport syndrome

Hunter syndrome

Ocular albinism

Adrenoleucodystrophy

41
Q

Signs of Fragile x syndrome

A

Causes mental retardation in some of males with this gene

learning disabilities, oversized ears, enlarged testes & double jointedness

may be involved with autism

Unaffected males may pass gene onto daughters whose children may suffer

42
Q

Name 4 common polygenic disorders

A

Alzheimer’s

Diabetes

Cancer

Eczema

43
Q

Define multifactorial inheritance

A

Inheritance controlled by many genes plus the effects of the environment

44
Q

The term for environmental influences that cause development defects

A

Teratogens

45
Q

Name 3 teratogens and what they affect

A

Chemicals & Drugs
Fetal alcohol syndrome = slow growth, facial features, defective heart & CNS
Cocaine = attention problems, hyperirritability, seizures

Cigarette Smoking
Low birth weight, cleft lip & palate, SIDS

Irradiation or radioisotopes during the first trimester
Mental retardation, microcephaly

Bioscience (4 decks)

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