Genetics Flashcards by Easy MRCOG

Which chromosome contains the gene that codes for the alpha globin chain (a constituent component of haemoglobin)?

Chromosome 16

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Chromosome replication happens in which phase

if not an option, choose Interphase which composed of (G1, S phase, G2)

S Phase

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What are the acrocenteric Chromosomes?

13, 14, 15, 21, 22

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Robertsonian Translocation

Chromosomal rearrangement involves fusion of long arms of 2 acrocentric chromosomes and loss of short arms.

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most common robertsonian translocations?

rob (13q:14q) and rob (14q:21q)

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Etiology of Down Syndrome

1ry Trisomy (non disjunction at meiosis) 95%
Robertsonian Translocation 14:21 3%
Mosaicism (1%)

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Mortality rate of Patau Syndrome

100% by age of 1 month

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Nuchal Translucency

sonographic appearance of subcutaneous fluid at the back of the fetal neck

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When nuchal translucency is perfomed?

11 to 14 weeks of gestation

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when to perform amniocentesis

after 15 weeks

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when to perform chorionic villus sampling

after 11 weeks of gestation

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when to perform cordocentesis

after 18 weeks of gestation
(with 1-2% risk of miscarriage)

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Congenital malformations with raised Alpfa feto protein

Neural Tube Defect (Spina bifida)
Omphalocele
Bladder Exstrophy
Intestinal Atresia

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Alfa feto protein levels in Down and Edward Syn.

Reduced

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Omphalocele is associated with

Patau Syn (T13)

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What percentage of first trimester miscarriages are thought to be attributed
to Turner Syndrome?

10-15%

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Hirschsprung’s disease is most commonly associated with?

Down Syn (T21)

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The five stages of mitosis in order are:

prophase, prometaphase, metaphase, anaphase, telophase

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The structure that indicates that crossing-over has occurred is the

chiasmata

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During oogenesis in humans, meiosis is blocked at which stage prior to ovulation?

diplontene stage of prophase 1

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The theory that the Barr Body is an inactivated X-chromosome is

the Lyon hypothesis

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If an affected male has all affected daughters but no affected sons, the trait is likely to be an

X-linked dominant trait

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If an affected male has affected daughters and sons in about the same number as unaffected daughters and sons, the trait is likely to be an

autosomal dominant trait

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What type of cell does mitosis create?

Diploid

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During anaphase of Meiosis, the chromosomes fail to separate properly This causes there to be an uneven amount distributed to the resulting daughter cells. What is this called?

Non-disjunction

Sister chromatids are joined together by

Centromeres

What is the genetic transmission of Marfans disease

Autosomal dominant

What are the most common serum markers that comprise the triple test?

Beta human chorionic gonadotropin (beta hCG), estriol alpha-fetoprotein (AFP)

A 46XY karyotype associated with female phenotype is found in

Testicular feminization syndrome ( ANDROGEN INSENSITVITY)

A baby with Down's syndrome ,the probability of extra chromosome 21 being maternal in origin is ?

80-85%

Which error in meiosis is the most common cause of Down syndrome?

Non-disjunction

What screening test has the highest detection rate for Down syndrome?

Stepwise sequential screening (Combined Test)

which is the most commonly describe inborn errors of metabolism that are diagnosable in utero?

Autosomal recessive disorders

Approximately what percentage of spontaneous first trimester abortions show chromosomal abnormalities?

50%

Which cells are typically used for pre-implantation genetic diagnosis?

Polar body from zygote

What disease is caused by a chromosome 5p deletion ?

Cri-du-chat syndrome

V' Shaped chromosomes are?

Telocentric

What effect does Down syndrome have on the quadruple test?

AFP: reduced uE3: reduced bhCG: elevated Inhibin A: elevated

Which enzyme deficiency may be associated with a female pt with karyotype 46XY?

5-alpha-reductase deficiency

The process by which mRNA is made from DNA is?

Transcription

What role does messenger RNA play in the synthesis of proteins?

Translation

What is the inheritance of sickle cell disease(SCD)?

autosomal recessive

The results of haemoglobin electrophoresis in a woman with sickle cell trait is

Haemoglobin A and haemoglobin S

Sickle cell disease is caused by

A mutation in the beta globin gene

With regard to the cell cycle. In what phase do nuclear envelopes form around daughter chromosomes?

Telophase

How many telomere are in the cell in metaphase of mitosis ?

Cell spends most of its time in which phase?

Interphase

What is the main infertility rate in cystic fibrosis patients?

98%

Male infertility in a patient with cystic fibrosis is most likely due to which condition?

Congenital absence of vas deference

male who has presented in infertility clinic with hypogonadism & Anosmia

kallman syndrome

Earliest most appropriate gestational age for chorionic villous sampling CVS to be done is.

11 weeks

The standard for convenQonal cytogeneQc analysis of human chromosomes is

G banding

Whenever the intestinal midgut loop fails to return from the umbilical cord into the abdominal cavity, the defect is known as

Omphalocele (exomphalos)

HbS rate in sickle cell trait

The usual partition of Hb A and Hb S in sickle cell trait is 60 : 40

Which one of the following stages of the cell cycle is cell prepared for DNA synthesis?

Gap phase 1 (G1)

Which one of the following stages of the cell cycle is preceded by mitosis?

Gap phase 2 (G2)

Which types of cells are phagocytic for residual bodies left over from the process of spermiogenesis

Sertoli cells

In which syndrome would a single barr body be found

Klienfilter syndrome

Malignant hyperthermia is recognized complication with the use of which drug

Suxamethonium

Which oncogen is associated with the development of breast cancer

HER-2

What is the action of restriction endonuclease

Bacterial enzyme which cleaves foreign DNA at a specific recognition site

What is the action of reverse transcriptase

Enzyme producing cDNA

What is the action of RNA Polymerase

Enzyme responsible for DNA transcription

What is the action of DNA polymerase

Enzyme responsible for DNA replication

What malignancy is associated with a defect in DNA gyrase

Xeroderma pigmentoza

What type of inheritance is Familial adenomatous polyposis

Autosomal Dominant

What is a commonest intra-abdominal childhood malignancy of primitive tubules and mesenchymal cells

Wilm’s tumor

In which type of malignancy are tumor suppressor genes MLH1 & MSH2 are found

Hereditary non polyposis colonic carcinoma (Lynch syndrome)

What type of inheritance of retinoblastoma

Autosomal Dominant

What type of inheritance of cystic fibrosis

Autosomal recessive

Patau syndrome is associated with

Omphalocele Holoprosencephaly Polydactyly

What chromosomal abnormality has an association with severely impaired semen quality

Microdeletion of the Y chromosome

Von willberand inherited as

Autosomal dominant

Hungtons chorea inherited as

Autosomal dominant

Duchenne muscular dystrophy inherited as

X linked recessive

How many genes included in mitochondrial DNA

37 genes

What percentage of down syndrome occur due to robertsonian translocation

Phenylketonuria is inherited as

Autosomal recessive

At the end of which phase of the cell cycle control mutation of genes

In which part of the cycle do Chromatids form?

S phase

Ash leaf spots, butterfly rash, Shagreen patches are features of?

Tuberous sclerosis

Life time risk of developing cancer of BRCA 2

Ovarian 15% Breast 45%

lifetime risk of breast cancer by mutated BRCA gene

12%

Chromosome abnormal in beta and delta thalassemia?

Chromosome 11

What type of inheritance pattern does Red Green Colour blindness follow

X-linked recessive

Which condition is caused by a chromosome micro deletion?

Cri‐du chat is a syndrome caused by micro deletion of chromosome 5 Like

Infantile Polycystic Kidney Disease is inherited as

autosomal recessive

Osteogenesis Imperfecta is inherited as

Autosomal dominant

What is the inheritance pattern of HNPCC (Lynch syndrome)?

Autosomal Dominant

What is the mode of inheritance of beta Thalassemia?

Autosomal recessive

Which fetal tissue is not typically used for karyotyping?

Fetal red blood cells

What percentage of fetuses with trisomy 21 detected by nuchal translucency scan alone?

10%

Possible number of codons?

risk of miscarriage following amniocentesis?

Cytosine pairs with

Guanine