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Exam In January > Genetics, Cogenital Anomalies And Prematurity > Flashcards

Genetics, Cogenital Anomalies And Prematurity Flashcards

1
Q

Chromosomes

A

Chromosomes contain deoxyribonucleic acid or DNA which holds the genetic information in chromosomes

Every somatic cell in the body contains 23 pairs of chromosomes = diploid cells

Hamsters contain 23 single chromosomes = haploid cells

22 pairs of chromosomes are autosomes (1 to 22) and 1 pairs are the sex chromosomes (XY or XX)

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2
Q

Karyotype

A

Is a test that identifies the size, standing and number of chromosomes in the body cells

X and Y chromosome means it’s a boy

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3
Q

Chromosome

A

Gene locus

P arm ( short arm )

Centromere

Homozygous gene pair

Heterozygous gene pair

Q arm ( long arm )

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4
Q

Deoxyribonucleic acid (DNA)

A

Chromosomes have a folded double helix structure and are located in the nucleus

The double helix holds a linear sequence of information in the form of base pairs

Bases on one strand compliment the bases on the other DNA strand

  • adenine : thymine (A-T, T-A)
  • cytosine : guanine (C-G, G-C)

Together our chromosomes contain 3 billion DNA bases

Mitochondria contains a small amount of DNA

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5
Q

DNA deoxyribonucleic acid

A

Alternating pentode sugar phosphate groups

Base pairs (A-G)

Cell
Nucleus
Supercooled DNA
Histones

Chromosomes are only visible when the cells are preparing to divide

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6
Q

What is a gene

A

A gene is a region of DNA that holds information that codes for a protein

DNA is a linear sequence of bases and a protein is a linear sequence-of amino acid

The correspondence between 3 base pairs and on amino acid is what is called the genetic code

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7
Q

From gene to protein

A

DNA is transcribed into RNA

RNA exits the nucleus

At a ribosome in the cytoplasm the DNA is translated into a protein

I.e DNA makes RNA and RNA makes protein

If there is a maturation in the DNA, the protein is either not made or the protein is abnormal - this is the basis of genetic diseases

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8
Q

Transcription of RNA from DNA

A

S

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9
Q

Proteins are folded linear molecules

A

Proteins are made up of one or more polypeptide molecules

Polypeptides are chains of amino acids

Functional proteins eg enzymes, hormones, haemoglobin

Structural proteins eg collagen, cytoskeleton

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10
Q

The human genome

A

Sequences in total in 2002

20000 protein coding genes per somatic cell

99.9% DNA bases identical in humans

Protein producing genes which account for about 1.5% of the genome

The rest of the DNA is associated with a number of functions but much is its functions is yet to be determined

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11
Q

Genetic terminology

A

Genotype : the genetic make up of a person

Phenotype : the physical characteristics, as determined by the genotype, eg blue eyes, dark hair, features that present as in a genetic disease

Pedigree: family tree detailing ages, sexes and disease history; aids prediction of how current or future individuals may be affected

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12
Q

Genetic terminology

A

Signal gene or monogenean can disorders

  • autosomal dominant
  • autosomal recessive
  • x linked recessive
  • Y linked
  • mitochondrial

Polygenic disorders

Multifactorial disorders

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13
Q

Genetic terminology

A

Heterozygous: a genotype with 2 different forms of a gene for example one normal one mutated

Homozygous a genotype with 2 identical forms of the gene for example both normal or both mutated

Penetrant was is a term used to describe the percentage chance of someone with the mutation actually developing the disease for example familial breast cancer due to mutations in the BRCA1 gene, females with a mutation in this gene have an 80% lifetime risk of developing breast cancer

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14
Q

Genetic terminology

A

Aneuplody is where there are an abnormal number of chromosomes, examples of these are

Monosomy is where there is one chromosome instead of two for example turners syndrome

Trisomy is where there are three chromosomes instead of two for example trisomy 21 Down’s syndrome

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15
Q

Genetic terminology

A

Single gene disease one mutated gene is the cause of disease Ed sickle cell diseases CF

Polygenic disease Several mutated genes are the cause of the disease for example diabetes

Multifactorial disease environmental influences for example hypertension

Genetic syndrome variety of common signs and symptoms leading to the disease phenotype for example Down syndrome

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16
Q

Genetic terminology

A

Mutations : permanent changes to the genetic information in an indivisible that usually means that the protein coded for is affected

Insertion - insertion of one or more base pairs

Deletion - deletion of one or more base pairs

Substitution - the same number of base pairs, but there is a critical change in the amino acid coded for

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17
Q

Patterns of inheritance

A

Dominant conditions : one of the two genes is mutated leading to disease for example Huntingdonshire disease

Recessive conditions both genes need to be mutated for the disease to occur; if only one is mutated, the individual is called a carrier for example CF or sickle cell anaemia

Sex linked disorders: arise due to mutated genes on the sex chromosomes for example haemophilia affects males, females and usually carriers

18
Q

Autosomal dominant

A

Require only one carrier parent of the dominant gene for child to acquire the disease

Eg
Achondroplasia
Osteogenesis imperfecta
Huntington’s disease

NB some case are new mutations

Father Hh (has one gene for Huntington’s)
Mother hh (normal genes)

Hh Hh Hh hh

19
Q

Autosomal recessive

A 
Father As (carrier)
Mother As (carrier)

AA As sA ss

Require two carrier parents for the child to acquire the disease

CF
Sickle cell disorders
Thalassaemia

20
Q

Sex linked inheritance for example haemophilia

A 
Father XY (unaffected)
Mother XXh (carrier)

XX girl

XXh girl

XY boy

YXh boy

21
Q

X linked disorders

A

Mutation occurs on the X chromosomes

Females are mainly carriers

Males inherit the disease

Eg duchenne muscular dystrophy, haemophilia

22
Q

Gene therapy

A

Much promise, but limited delivery to date

Challenge is getting a gene or genes into cells and the genome of the affected individual

More potential when treating an early stage embryo

Ethical and legal issues to be considered the idea of designer babies is regularly seen in the press

23
Q

Summary

A

Genetics is icreasiningly recon gnoses as the cause of or is contributory to illness

The function of DNA and the genome continues to be research- the holy grail is a cure for genetic diseases

It is important to have a working knowledge of genetic terminology and patterns of inheritance for clinical work

24
Q

Embryonic development and congenital anomalies

Terminology

A

Haploid cells - containing 23 signal chromosomes (sperm and ovum)

Diploid cell - cells contains 23 pairs of chromosomes

Zygote - the diploid cell produces at conception before further cell division

Embryo - the baby during the first 2 months

Foetus- after the first 2 months and when the individual organs are identifiable

25
Q

Early stage of development

A

Ovum

Fertilisation

Fusion of egg and sperm pronuclei

Zygote become one before dividing

Cleavage 2 then 4 then 8 called

Morula

Blastocyst

Implanted blastocyst

26
Q

Early stages of development

A

At 15 days post fertilisation, three different germ layers have formed

Ectoderm

Mesoderm

Endoderm

Each give rise to major components of specific body structures and organs

27
Q

Ectoderm

A

Ectoderm goes onto form

Skin, nails, hair follicles, sweat glands, and nerves within the lungs

Neuroectoderm is a special subdivision of ectoderm that goes onto form

Brain, spinal cord and peripheral nerves, as well as many of the muscles and bones of the face

28
Q

Mesoderm

A

Mesoderm Goes onto form

Heart, kidneys, bones, muscles and blood vessels, as well as part of the reproductive and urinary system

29
Q

Endoderm

A

Endoderm goes onto form

Digestive tract, respiratory tract and glandular epithelium

30
Q

Cogenital anomalies

A

Microcephaly

Hydrocephaly

Spinal bifida

31
Q

Development of the face

A

Cleft lip and palate

1: 1000

32
Q

The foetal heart

A

By 22 days, the embryonic heart begins to beat

The heart develops four chamber, although the circulation through the embryonic heart is different from that of postnatal life

33
Q

Congenital heart defects

A

Atrial septal defect

Hole into the right and left atrium

Ventricular septal defect

Hole into the right and left ventricle

34
Q

Cogenital heart defects

A

Tetralogy of fallot

Coarctation of the aorta

35
Q

Cogenital anomalies in the chest

A

Diaphragmatic hernia

Intestine protruding through hole in diaphragm

Tracheo-oesophageal fistula

36
Q

Cogenital anomalies of the GIT

A

Exomphalous

Gastrishisis

37
Q

Examples of congenital renal anomalies

A

Bladder extrophy

Horse shoe kidney

Renal agenesis

38
Q

Screening for foetal anomalies

A

A screening test can find out if a baby has a high or low chance of having a particular health problem

They cannot usually tell for certain if the baby is affected, but they give a risk rating and from there further testing can be considered

Such test during pregnancy are aimed at helping expectant mothers and fathers make choices about care or treatment during the pregnancy and or after the baby is born

39
Q

Screening for foetal anomalies

A

Current screening includes

Ultrasound scans

  • 13 weeks gestation: looks at Michal fold, nasal bridge, cardiac anatomy
  • 20 weeks gestation: more detail of the organs and limbs, and where the placenta is in the uterus

Blood test
- quad screen test includes test for alphafetoprotin, uncojugated oestruol, human chorionic gonadotropin and inhibit-A

40
Q

New born screening

A

Heart, eyes, hips and testes (physical examination)

Hearing- to identify sensorineural hearing loss

Blood spot - sickle cell disease, CF, congenital hypothyroidism, a range of inherited metabolic disorders

41
Q

Summary

A

Conception through embryogenesis to being born is a complex process

Significant cogenital anomalies can be life changing, life limiting or incompatible with life

Many will require medical and surgical interventions and then long term support

Improvements in antenatal diagnosis means that there is a need for counselling to help support parents

Exam In January (11 decks)

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