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RED > L18: Genetics > Flashcards

L18: Genetics Flashcards

1
Q

What is a chromosome

A

Made of a single molecule of DNA

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2
Q

What is a gene

A

A specific stretch of DNA where the sequence contains the genetic instruction to make a protein.

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3
Q

How many genes does one chromosome have

A

Hundreds of genes

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4
Q

What are the 2 types of cell division

A

Mitosis

Meiosis

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5
Q

What does mitosis procure

A

Identical daughter cells

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6
Q

What does meiosis produce

A

Haploid gametes

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7
Q

Describe the process of meiosis

A

1) replicate DNA
2) meiosis 1 division with crossing over and recombination
3) meiosis 2 division
4) this results in 4 haploid gametes

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8
Q

What are the 2 purposes of meiosis

A

Reduce chromosome number

Promote genetic diversity through re-assortment of genes where chromosomes cross over

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9
Q

What are the 2 stages where error in meiosis can appear

A

DNA replication

Meiotic cells division

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10
Q

What type of error would dna replication give rise to

A

New mutations (copying errors)

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11
Q

What type of errors would meiotic cell division five rise to

A

Anomalies in chromosome number

Anomalies in chromosome structure due to unequal crossing over

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12
Q

What are the classes of genetic disorder

A

Single gene disorders
Multifactorial disorders
Chromosomal disorders
Mitochondrial

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13
Q

What are single gene disorders

A

Mutation in the single gene that affects the function of the gene so it produces a faulty protein

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14
Q

What are multifactorial disorders

A

Variants within multiple genes that have minor effects but come together with the environment to cross the threshold to cause disease

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15
Q

What is chromosomal disorders

A

Genes themselves are normal but there is a dosage problem e.g trisomy

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16
Q

What type of mutations can occur in single gene disorders

A 
Missense 
Nonsense 
Frameshift 
Duplication 
Deletion 
Insertion
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17
Q

What is missence mutation

A

Where you have a substitution of a single base e.g swap b to c, it can either change the protein are does not because the code is degenerative

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18
Q

What is frameshift mutation

A

Insertion or deletion less than 3 base so whole reading frame is altered

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19
Q

What are the 2 subtypes that we can classify chromosomal anomalies into

A

Numerical

Structural

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20
Q

What are the numberical chromosomal disorders

A

Aneuploidy

Polyploidy

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21
Q

What does aneuploidy chromosomal disorders give rise to

A

Monosomy

Trisomy

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22
Q

What does polyploidy chromosomal disorders give rise to

A

Triploidy

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23
Q

What are the structural chromosomal disorder types

A

Translocation
Deletion
Duplication
Inversion- turned by 180 degrees

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24
Q

What are the 2 types of translocation that can occur

A

Reciprocal

Robertsonian

25
Q

What are the 3 most common trisomy chromosomal disorders that occur in the new born

A

Trisomy 21= Down’s syndrome
Trisomy 18= edwards syndrome
Trisomy 13= patau syndrome

26
Q

What are the common numerical chromosome disorders that occur in sex chromosome

A

Turners syndrome 45 X

Klinefelters syndrome 47 XXY

27
Q

If an individual is affected by a condition what type of symbol are they on a pedigree

A

Shaded

28
Q

What is the symbol that represent a male on a pedigree

A

Box

29
Q

What is the symbol that represents a female on the pedigree

A

Circle

30
Q

What symbol represents marriage on a prefigure

A

Horizontal line connecting the box and circle

31
Q

What symbol represents consanguineous couples

A

Double horizontal line

32
Q

What does consanguinity mean

A

Couples that are related other than marriage e.g causing that are married

33
Q

What are the factors that increase the risk of pregnancy genetic disorder

A 
Family history of the genetic disorder
Parental consanguinity 
Population ancestry of parents 
Increased maternal age 
Increased paternal age 
Environmental exposure to DNA
34
Q

What type of condition is cystic fibrosis

A

Autosomal recessive

35
Q

If 2 couples are both carriers for CFTR gene what are the possible outcomes in the offspring

A

Unaffected
2 carrier
1 affected

36
Q

Therefore What is the chance of CF affecting the pregnancy

A

1/4

37
Q

If a couple does not have a family history of CF what is there chance for being a carrier

A

Same as the rest of the population i.e 1 in 23 (1/23)

38
Q

If there is a recessive condition in the family what does consanguinity increase the risk of

A

Carrier

39
Q

What are the 2 types of translocations

A

Robertosnian

Reciprocal

40
Q

What is robertsonian translocation

A

When you get a fusion of the centromeres of the short and long arm between specific chromosomes of (13,14,15,21,22)

41
Q

What is reciprocal translocation

A

When you have a break in 2 chromosome which exchange fragments

42
Q

What is balanced reciprocal translocation

A

When the chromosome breaks and joins to another, it is balanced because the fragments switch places and all the genetic material is still there

43
Q

What can balanced recipricol translocation result in

A

Balanced carrier

44
Q

What zygote does balanced recipriocla translocation carrier form with normal gametes at fertilisation

A

1 Normal
1 balanced carrier
2 partial trisomy and partial monosomy

45
Q

What does partial monosomy and partial trisomy have a risk of

A

Miscarriage
Congenital malformation
Developmental delay
Intellectual disability

46
Q

Why is it important to know the ancestral population of a person

A

Because some genetic condition are more common in certain ancestors

47
Q

Why does the risk of genetic disorders increase with increased maternal age

A

When an egg ovulates it is in meiosis 1 block until fertilisation occurs so meiosis 2 happens. The length interval for meiosis increases the risk of spindle formation so you can get non-disjunction effect

48
Q

What does non disjunction result In

A

An egg having 2 chromosome instead and of 1 so when it joins with the sperm that has 1 chromosome this results in trisomy.

49
Q

Why does the risk of genetic disorders increase with increased paternal age

A

1) When sperm is produced one spermatogonium remains behind to maintain the division and divide
2) older the sperm is the more cell division it has gone through
3) it has replicated DNA more often so you increase the risk of mutation i.e single gene disorders

50
Q

On a pedigree how does a gene disorder look like if the cause is due to increased paternal age

A

Only one child is affected

51
Q

Name a condition that is due to elevated paternal age

A

Achondroplasia

52
Q

What are the option available for couples with increased genetic disorder

A 
Adoption 
Postpone pregnancy 
Accept the risk 
Prenatal diagnosis 
Artificial insemination by donor egg/sperm
53
Q

What does prenatal diagnosis involve

A

Ultrasound scanning
Chorionic villus sampling
Amniocentesis
Non invasive blood testing

54
Q

What does ultrasound scanning look at

A

Structural anomalies at 20 weeks

55
Q

What does chorionic villus sampling involve

A

You collect a chorionic villus sample and look at the chromosome of the baby

56
Q

What is amniocentesis

A

You take a sample of the amniocentesis and look at babies chromosome of dna

57
Q

What is non invasive genetic testing

A

A blood test as fetal blood circulates in maternal blood

58
Q

What are the 2 methods of non invasive genetic testing for x linked conditions

A

Fetal sexing

59
Q

What is the method of non invasive genetic testing for trisomy 21/18/13

A

NIPT (screening not definite diagnosis)

RED (19 decks)

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