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L18: Genetics Flashcards

(59 cards)

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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

Study These Flashcards
A

Reciprocal

Robertsonian

25
What are the 3 most common trisomy chromosomal disorders that occur in the new born
Trisomy 21= Down’s syndrome Trisomy 18= edwards syndrome Trisomy 13= patau syndrome
26
What are the common numerical chromosome disorders that occur in sex chromosome
Turners syndrome 45 X | Klinefelters syndrome 47 XXY
27
If an individual is affected by a condition what type of symbol are they on a pedigree
Shaded
28
What is the symbol that represent a male on a pedigree
Box
29
What is the symbol that represents a female on the pedigree
Circle
30
What symbol represents marriage on a prefigure
Horizontal line connecting the box and circle
31
What symbol represents consanguineous couples
Double horizontal line
32
What does consanguinity mean
Couples that are related other than marriage e.g causing that are married
33
What are the factors that increase the risk of pregnancy genetic disorder
``` Family history of the genetic disorder Parental consanguinity Population ancestry of parents Increased maternal age Increased paternal age Environmental exposure to DNA ```
34
What type of condition is cystic fibrosis
Autosomal recessive
35
If 2 couples are both carriers for CFTR gene what are the possible outcomes in the offspring
Unaffected 2 carrier 1 affected
36
Therefore What is the chance of CF affecting the pregnancy
1/4
37
If a couple does not have a family history of CF what is there chance for being a carrier
Same as the rest of the population i.e 1 in 23 (1/23)
38
If there is a recessive condition in the family what does consanguinity increase the risk of
Carrier
39
What are the 2 types of translocations
Robertosnian | Reciprocal
40
What is robertsonian translocation
When you get a fusion of the centromeres of the short and long arm between specific chromosomes of (13,14,15,21,22)
41
What is reciprocal translocation
When you have a break in 2 chromosome which exchange fragments
42
What is balanced reciprocal translocation
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
What can balanced recipricol translocation result in
Balanced carrier
44
What zygote does balanced recipriocla translocation carrier form with normal gametes at fertilisation
1 Normal 1 balanced carrier 2 partial trisomy and partial monosomy
45
What does partial monosomy and partial trisomy have a risk of
Miscarriage Congenital malformation Developmental delay Intellectual disability
46
Why is it important to know the ancestral population of a person
Because some genetic condition are more common in certain ancestors
47
Why does the risk of genetic disorders increase with increased maternal age
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
What does non disjunction result In
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
Why does the risk of genetic disorders increase with increased paternal age
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
On a pedigree how does a gene disorder look like if the cause is due to increased paternal age
Only one child is affected
51
Name a condition that is due to elevated paternal age
Achondroplasia
52
What are the option available for couples with increased genetic disorder
``` Adoption Postpone pregnancy Accept the risk Prenatal diagnosis Artificial insemination by donor egg/sperm ```
53
What does prenatal diagnosis involve
Ultrasound scanning Chorionic villus sampling Amniocentesis Non invasive blood testing
54
What does ultrasound scanning look at
Structural anomalies at 20 weeks
55
What does chorionic villus sampling involve
You collect a chorionic villus sample and look at the chromosome of the baby
56
What is amniocentesis
You take a sample of the amniocentesis and look at babies chromosome of dna
57
What is non invasive genetic testing
A blood test as fetal blood circulates in maternal blood
58
What are the 2 methods of non invasive genetic testing for x linked conditions
Fetal sexing
59
What is the method of non invasive genetic testing for trisomy 21/18/13
NIPT (screening not definite diagnosis)

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