Genetics Flashcards
Which chromosome contains the gene that codes for the alpha globin chain (a constituent component of haemoglobin)?
Chromosome 16
Chromosome replication happens in which phase
if not an option, choose Interphase which composed of (G1, S phase, G2)
S Phase
What are the acrocenteric Chromosomes?
13, 14, 15, 21, 22
Robertsonian Translocation
Chromosomal rearrangement involves fusion of long arms of 2 acrocentric chromosomes and loss of short arms.
most common robertsonian translocations?
rob (13q:14q) and rob (14q:21q)
Etiology of Down Syndrome
- 1ry Trisomy (non disjunction at meiosis) 95%
- Robertsonian Translocation 14:21 3%
- Mosaicism (1%)
Mortality rate of Patau Syndrome
100% by age of 1 month
Nuchal Translucency
sonographic appearance of subcutaneous fluid at the back of the fetal neck
When nuchal translucency is perfomed?
11 to 14 weeks of gestation
when to perform amniocentesis
after 15 weeks
when to perform chorionic villus sampling
after 11 weeks of gestation
when to perform cordocentesis
after 18 weeks of gestation
(with 1-2% risk of miscarriage)
Congenital malformations with raised Alpfa feto protein
Neural Tube Defect (Spina bifida)
Omphalocele
Bladder Exstrophy
Intestinal Atresia
Alfa feto protein levels in Down and Edward Syn.
Reduced
Omphalocele is associated with
Patau Syn (T13)
What percentage of first trimester miscarriages are thought to be attributed
to Turner Syndrome?
10-15%
Hirschsprung’s disease is most commonly associated with?
Down Syn (T21)
The five stages of mitosis in order are:
prophase, prometaphase, metaphase, anaphase, telophase
The structure that indicates that crossing-over has occurred is the
chiasmata
During oogenesis in humans, meiosis is blocked at which stage prior to ovulation?
diplontene stage of prophase 1
The theory that the Barr Body is an inactivated X-chromosome is
the Lyon hypothesis
If an affected male has all affected daughters but no affected sons, the trait is likely to be an
X-linked dominant trait
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
What type of cell does mitosis create?
Diploid
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 ?
4
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
3%
Phenylketonuria is inherited as
Autosomal recessive
At the end of which phase of the cell cycle control mutation of genes
G1
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?
64
risk of miscarriage following amniocentesis?
1%
Cytosine pairs with
Guanine
