Genetics

Question 1

Each human has how many pairs of chromosomes?

Answer 1

23 pairs in total

22 autosomal pairs, 1 sex-linked pair

Question 2

G0 phase of the cell cycle

Answer 2

Most cells are resting, carrying out their normal function

Question 3

G1 phase of the cell cycle

Answer 3

1st growth phase as chromosomes become ready to be replicated

Question 4

S phase of the cell cycle

Answer 4

DNA replication occurs

Question 5

G2 phase of the cell cycle

Answer 5

2nd growth phase involving proteins etc.

Question 6

M phase of the cell cycle

Answer 6

Mitosis - mechanical separation of cell into two daughter cells
Two daughter cells are identical, diploid cells

Question 7

Variation occurs during meiosis by two main methods, which are?

Answer 7

Crossing over

Independent segregation of homologous chromosomes

Question 8

In meiosis, one diploid cell becomes…

Answer 8

Four haploid daughter cells

Question 9

Examples of sequence variations between genes?

Answer 9

Single nucleotide polymorphisms (SNPs)

Deletions/duplications

Question 10

A polymorphism is…

Answer 10

A change in the genome that does not cause disease in its own right, but can predispose to a common disease

Question 11

Chromosome 22 looks like a…

Answer 11

Teddy bear

Question 12

A chromosome consists of…

Answer 12

Telomeres at each end
Short arm (p)
Centromere
Long arm (q)

Question 13

A chromosome is metacentric if…

Answer 13

Both arms are roughly the same length

Question 14

A chromosome is acrocentric if…

Answer 14

The p (short) arm is so short it is hard to observe

Question 15

A chromosome is telocentric if…

Answer 15

The centromere is located at the terminal end of the chromosome

Question 16

An aneuploidy is…

Answer 16

An abnormal number of chromosomes
Monosomy - missing chromosome from one pair
Trisomy - extra chromosome in a pair

Question 17

Reciprocal translocations are when…

Answer 17

Segments from two different chromosomes have been exchanged

Question 18

Robertsonian translocations are when…

Answer 18

A chromosome attaches to another chromosome at the centromere
Only occurs with 13, 14, 15, 21, 22

Question 19

Monosomy of the sex chromosomes causes…

Answer 19

Turner’s syndrome

Question 20

Trisomy of chromosome 21 causes…(means there are three copies of chromosome 21 instead of the normal two copies)

Answer 20

Down’s syndrome

Question 21

What is FISH?

Answer 21

DNA probes specifically bind to areas of individual chromosomes and apply a fluorescein stain to make the chromosome visible
Useful for detecting aneuploidies

Question 22

Penetrance is defined as…

Answer 22

The likelihood of having the disease given you have the genetic mutation

Question 23

Mendelian inheritance encompasses which disorders?

Answer 23

Autosomal dominant
Autosomal recessive
X-linked
Mitochondrial disorders

Question 24

Autosomal dominant disease occurs when…

Answer 24

Autosomal dominant disease occurs when there is a single copy of the faulty gene, seen in all generations, and has a 50% risk of affecting the child if the parent is affected. Examples include Huntington’s disease and Marfan syndrome.

Question 25

Autosomal recessive disease occurs when…

Answer 25

Autosomal recessive disease occurs when an individual inherits two copies of the mutated gene, one from each parent. It often only affects one generation of a family and has a 25% risk of affecting the child if both parents are carriers. Examples include cystic fibrosis and sickle cell anemia.

Question 26

X-linked disease occurs when…

Answer 26

X-linked disease occurs when there is a mutation in a gene on the X chromosome. The inheritance pattern is different for males and females, with males being more commonly affected and females being carriers.

Question 27

Mitochondrial disease occurs when…

Answer 27

Diseased mitochondria passed from mother to child

Question 28

What is mosaicism?

Answer 28

Occurs when cells within the same person have a different genetic makeup. e.g cancer

Question 29

Epigenetic variation describes…

Answer 29

Epigenetic variation refers to changes in how genes are expressed and function, without changing the underlying DNA sequence. These changes can be influenced by things like the environment and lifestyle, and can affect traits and disease susceptibility. These variations can be inherited from one generation to the next and studying them can help us understand how our genes and environment interact to affect our health and well-being.

Question 30

Methylation inhibits which process?

Answer 30

DNA transcription

Methylation is an epigenetic modification that involves the addition of a methyl group to a cytosine base in DNA, and this modification can interfere with the binding of transcription factors and other proteins to the DNA, thereby preventing the initiation of transcription.

Question 31

What is imprinting?

Answer 31

Variation in gene expression depending on which parent you inherit the gene from
e.g. in Angelman’s syndrome, mother’s UBE3A works fine but father’s is methylated

Question 32

Heteroplasmy is when…

Answer 32

Different daughter cells contain different proportions of mutant mitochondria (similar to mosaicism)

Question 33

Where are the 2 checkpoints in the cell cycle where DNA can acquire mutations?

Answer 33

Between G2 and M

Between G1 and S

Question 34

What is the function of oncogenes?

Answer 34

Promote cell division

Question 35

What is the function of tumour suppressors?

Answer 35

Inhibit cell division

Question 36

Only one copy of the tumour suppressor gene is required to be mutated for cancer to occur. True/False?

Answer 36

False

2 copies required

Question 37

Cancer is most often inherited as a high penetrance Mendelian disorder. True/False?

Answer 37

False. Cancer is most often not inherited as a high penetrance Mendelian disorder. Instead, most cancers are caused by a combination of genetic and environmental factors, and are considered multifactorial disorders. Only a small percentage of cancers are caused by high-penetrance inherited mutations in specific genes, such as BRCA1 and BRCA2 mutations in breast and ovarian cancer.

Question 38

This disease is acquired through co-dominant inheritance

Answer 38

(Sickle cell anaemia) All blood is co-dominant inheritance e.g. type AB are two equally dominant gene expressions of blood type.

if an individual inherits two different alleles for a particular gene, neither allele is dominant or recessive over the other, and both are expressed in the phenotype.

For example, in the case of blood type, the A and B alleles are co-dominant. If an individual inherits one A allele and one B allele, they will express both A and B antigens on their red blood cells, resulting in blood type AB. Neither the A nor the B allele is dominant over the other, so both are expressed equally in the phenotype.

Similarly, in sickle cell anemia, the HbA and HbS alleles are co-dominant. If an individual inherits one HbA allele and one HbS allele, they will produce both normal hemoglobin and abnormal hemoglobin in their red blood cells, resulting in the symptoms of sickle cell anemia.

Question 39

A patient with this disease has 49 chromosomes

Answer 39

(Klienfelter Syndrome) Patients with Klienfelter’s have 3 sex chromosomes (47 XXY) and so they have in 49 total

Question 40

Multifactorial inheritance

Answer 40

If parent has cancer, likely to have multiple polymorphisms that confer to a small additional risk for that condition.

Question 41

the amount of protein produced is determined by

Answer 41

1. rate of transcription (mRNA making)
2. rate of splicing to mRNA
3. Half life of mRNA
4. Rate of processing polypeptide

Question 42

what is the difference between amniocentesis and direct genetic testing

Answer 42

amniocentesis for a fetus, or directly for a specific condition in a child or adult.

Question 43

antenatal testing for —-

Answer 43

Down’s syndrome.

Question 44

What is predictive testing in genetics?

Answer 44

Predictive testing involves testing a person for a specific gene mutation that has implications for them in the future. Examples include the BRCA1 breast cancer gene or the gene for Huntington’s chorea.

Question 45

What is carrier testing in genetics?

Answer 45

A: Carrier testing involves testing parents or potential parents for the gene for a specific autosomal recessive condition in order to calculate the risk of passing it to their children. An example of this is testing for the cystic fibrosis gene.

Question 46

What are some ethical issues to consider when performing genetic testing?

Answer 46

A: There are significant ethical implications for genetic testing, and it is essential to obtain consent and perform genetic counseling before doing the test. The greater the implications of the test, the more genetic counseling will be required.

Question 47

What is karyotyping in genetics testing?

Answer 47

A: Karyotyping involves looking at the number of chromosomes, their size, and basic structure. This is helpful in diagnosing conditions like Down’s syndrome and Turner syndrome.

Question 48

What is microarray testing in genetics?

Answer 48

A: Microarray testing involves cutting up the genetic material from an individual using enzymes, applying it to a plate, and separating molecules of different weights into different locations. This can be used to see what genes the person expresses, screen for chromosomal abnormalities and many common genetic conditions, and look for mutations in cancer cells.

Question 49

What is specific gene testing in genetics?

Answer 49

A: Specific gene testing can be done by splitting the two strands of DNA and adding a “gene probe” that contains complementary genetic code for a specific gene you want to test for. This is used to confirm whether a patient has a particular gene.

Question 50

What is DNA sequencing in genetics?

Answer 50

A: DNA sequencing is used for research purposes and involves splitting the two strands of DNA and revealing the exact sequence of nucleotides in that section of DNA. It has no role in routine clinical practice.

Question 51

Array CGH

Answer 51

is a high-resolution technique used for the detection of copy number variations (CNVs), which are known to be associated with intellectual disability, developmental delay, and congenital anomalies.

Question 52

PCR and Sanger sequencing

Answer 52

are useful for detecting point mutations or small insertions and deletions in specific genes.

Question 53

Which genetic abnormalities most commonly causes Down’s Syndrome?

Answer 53

Nondisjunction is the most common genetic abnormality that causes Down’s Syndrome. Nondisjunction occurs when the chromosomes fail to separate properly during meiosis, resulting in one gamete (egg or sperm) receiving an extra copy of chromosome 21

Question 54

genetic conditions occurs due to genetic imprinting where the gene is deleted from the father?

Answer 54

Prader-Willi syndrome

Question 55

Definition of incidence

Answer 55

New cases of a disease occurring in a population in a defined time period

Question 56

heterozygous

Answer 56

1 in 4 is being affected
Recessive dominate (both parents are carrier )
e.g cystic fibrosis

Question 57

characteristic of an X-linked recessive disorder?

Answer 57

C. There is no male to male transmission of the condition

Question 58

D. del(5q), del(17p), trisomy 8

Answer 58

The long arm of a chromosome is referred to as ‘q’ and the short arm as ‘p’. An extra copy of a chromosome is termed ‘trisomy’ and loss of an entire chromosome is ‘monosomy’.

Question 59

Robertsonian translocation

Answer 59

is the centric fusion of two acrocentric chromosomes resulting in the formation of one large metacentric chromosome and one small fragment.

Question 60

45 X

Answer 60

Turner syndrome is characterised by the absence of an X chromosome.

Question 61

A. Edward syndrome

Answer 61

47 XY +18

Question 62

Many PRR are lectin-like

Answer 62

in that they recognize exposed microbial sugars

Question 63

In genetic tree if both male and females are effected then its most likely to be

Answer 63

Autosomal dominant

THUS no chance for a carrier

Question 64

If only womens are effected in genetic tree than is most likey

Answer 64

recessive disorder

50% chance to be a carrier

Question 65

Anticipation

Answer 65

is the phenomenon in which the age of onset of a condition lowers with each successive generation. (how early in his age will he show the symptoms of the genetic defect )Classically this is seen in trinucleotide repeat disorders such as Huntington’s disease (CAG expansion), myotonic dystrophy (CTG), and fragile X-syndrome (CGG), and is caused by the repeated trinucleotide expanding further in each successive generation.