Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

MCD Year 1 > Genetics > Flashcards

Genetics Flashcards

1
Q

What is a malformation and give one example?

A

A primary structural defect, usually involving a single organ showing multifactorial inheritance
e.g. cleft lip

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a disruption and give one example?

A

Secondary abnormal structure of an organ or tissue caused by ichaemia, infection or trauma. Not genetic but genetic factors can predispose
e.g. amniotic band causing digital amputation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a deformation and give one example?

A

Abnormal mechanical force distorting a naturally formed structure. Occurs late in pregnancy and has good prognosis as the organ is normal in structure, just physically malformed
e.g. club foot, hip dislocation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a syndrome and give one example?

A

A consistent pattern of abnormalities with a specific underlying cause, usually genetic
e.g. Down’s syndrome (chromosomal abnormality)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a sequence and give one example?

A

Multiple abnormalities initiated by a primary factor. Could have genetic component as initial factor
e.g. Potter sequence
Oligohydramnios= reduced amniotic fluid volume due to a failure to produce urine which is classically due to bilateral renal agenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a dysplasia and give one example?

A

An abnormal organisation of cells into tissues
e.g. Thanatophoric dysplasia= severe skeletal disorder characterised by extremely short limbs and folds of extra skin on the arms and legs as well as a large head and a small thorax. Caused by a single gene defect in the FGFR3 gene and carries a high recurrance in siblings and offspring of the affected person.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is an association and give one example?

A

A non-random occurrence of abnormalities not explained by a syndrome. Cause is typically unknown
e.g. VATER association (Vertebral Anal Tracheal Oesophageal Renal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a dysmorphism and give one example?

A

An unusual or abnormal physical feature (sometimes as part of a genetic syndrome)
e.g. Hypertelorism- an abnormality which results in an increased distance between two organs (e.g. eyes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What risks are associated with advanced maternal age? What age is this?

A

Women over the age of 35 at the time of delivery have an increased risk of having an infant with a chromosomal abnormality.
This is classed as the advanced maternal age because at this age the risk of a chromosomal abnormality exceed the risk of a complication from amniocentesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the risks associate with advanced paternal age?

A

Advanced paternal age is associated with higher risk of certain single gene disorders eg achondroplasia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the human karyotype?

A

Diploid number= 22 autosomes and 1 sex chromosome from each parent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the three types of chromosome?

A

Metacentric- Two equally long arms
Submetacentric- One set of “short arms”
Acrocentric- One set of chromatids virtually non-exisent, but rather seen as “satellites”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a numerical chromosomal abnormality?

A

Aneuploidy, loss or gain (change in total number)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a structural chromosomal abnormality?

A

Translocation, deletions, insertions, inversions or rings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a mosaicism chromosomal abnormality?

A

Different cell lines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is monosomy?

A

The loss of a single chromosome. It is almost always lethal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is trisomy?

A

Gain of one chromosome. It can be tolerated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is tetrasomy?

A

Gain of two chromosomes. It can be tolerated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is a balanced translocation?

A

It is the “swap of areas” on a chromosome. They are still normal length so it is unlikely to have a significant effect.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is an unbalanced translocation?

A

The swap results in the translocation result in chromosomes that are not of normal length. The total DNA on each chromosome is not equal so more likely to have disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What mutation causes Down Syndrome?

A

Trisomy of chromosome 21

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the clinical features of Down Syndrome?

A

Macroglossia (enlarged tongue), small ears, epicanthic folds, upward sloping palpebral fissures, Brushfield spots, single palmar crease, wide gap between first and second toes, A and V septal defects, short stature and duodenal atresia.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What causes trisomy 21 in Down Syndrome

A

95% of cases caused by a nondisjunction in meiosis (not splitting properly)
4% of cases caused by translocations; the breakage of acrocentric chromosomes and fusion of their long arms
1% of cases caused by mosaicism; occurs after the zygote is formed and depending on when is has occurred you can determine the proportion of affected cells in the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Give two examples of common sex chromosome aneuploidies?

A

Turner’s syndrome (monosomy X)

Polysomy X in females (47, XXX)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Give two examples of common autosomal chromosome aneuploidies?
``` Down syndrome (trisomy 21) Edward's syndrome (trisomy 18) ```
26
What is dosage compensation with relation to chromosomes?
The equalisation of gene expression between the males and females of a species. Females silence the transcription of one X chromosomes and transcribe all the information from the other
27
What causes an individual to be chromosomally one gender but phenotypically another?
An abnormality involving the SRY gene
28
Explain what occurs to result in XX males?
Translocation of the SRY male determining gene from the Y chromosome to an X chromosome. Phenotypically male, testes develop, but sterile because some genes on Y chromosome needed for spematogenesis
29
Explain what occurs to result in XY females?
Mutations or deletions of SRY gene leads to phenotypically female who is infertile
30
What possible meiotic products can result from someone with a balanced translocation?
50% normal or balanced | 50% unbalanced
31
Give two examples of genomic disorders?
Di George Syndrome | Cri du Chat Syndrome
32
What is a genomic disorder?
The loss of gain of genetic material
33
What is recurrent microdeletion disorder?
A very small deletion in a DNA sequence
34
What is a monogenic disorder, how are they passed on, are they rare?
They are familial, have a specific mode of inheritance and can be common or rare
35
What is a complex disorder, how are they passed on, are they rare?
The effects of multiple genes in combination with lifestyle and environmental factors. No clear cut pattern of inheritance. They can be sporadic. Cause of many common disorders such as type II diabetes, obesity, Parkinson's
36
What is Mendelian inheritance?
The process whereby individuals inherit and transmit to their offspring one out of the two alleles present in homologous chromosomes
37
What is an allele?
The alternate forms of a gene or DNA sequence at the same locus
38
What are homologous chromosomes? Do they contain the same alleles?
They are a matching, non-identical pair of chromosomes. One is inherited from each parent. They can have different alleles
39
What is a polymorphism?
The occurrence of a chromosome or genetic characteristic in more than one form, which results in the coexistence of different phenotypes within a population eg different hair colours.
40
What is a mutation?
Heritable change in DNA sequence. This is a change in the genotype which has a definite effect on the phenotype
41
What is a missense mutation?
A point mutation (a change in a single base pair) which codes for a different amino acid. Does not definitely affect the protein function
42
What is a nonsense mutation?
A point mutation which results in the formation of a stop codon which leads to premature termination of the polypeptide chain; this can have a significant effect of protein function
43
What is an insertion?
Insertion of a nucleotide can create a frame shift as the genetic code is read in triplets. Can result in a completely different protein being made
44
What is a deletion?
Can also create a frame shift- but if 3 base pairs were deleted it may have no effect
45
What is dominance?
The effect of an allele which will control the phenotype
46
What is codominance?
Where both alleles are equally strong and are both visible in the genotype
47
What is dominant anticipation?
The increase in severity and/or earlier onset of symptoms in each generation eg Huntington Disease (unstable CAG which may expand with each generation)
48
What is an autosomal dominant disorder? Who does it affect, how is it transmitted, what probability will the disease be passed on to the next generation? Give one example.
At least one parent is affected, it does not skip generations. It is transmitted by males of females and both genders can be affected. It has verticle transmission. A child of an individual with an autosomal dominant disorder has a 50% chance of being affected e.g. Huntington disease
49
What is an autosomal recessive disorder? Who does it affect, how is it transmitted, what is the probability the disease will be passed on to the next generation? Give one example.
No affected parent. Transmitted by both males and females and both genders can be affected. Usually no family history. If both parents are carriers there is a 25% chance their child will have the disease, a 50% chance their child will be a carrier and a 25% chance they will be normal. e.g. Cystic fibrosis
50
What is an X-Linked disorder? Who does it affect, how is it transmitted, what is the probability the disease will be passed on to the next generation? Give one example.
No affected parents. Males are affected but it is transmitted by carrier females. 50% of sons are affected if the mother is a carrier and 50% of daughters will be a carrier. Caused by a mutation on the X chromosome. Majority are recessive but there is no homologous section on the Y chromosome for men. e.g. Haemophilia A
51
What is genetic heterogenity?
Single phenotype or genetic disorder may be caused by a multiple number of alleles or non-alleles (locus) mutations
52
What is penetrance?
The frequency with which symptoms are present in an individual who inherits a disease causing mutation The frequency of phenotype associated with a particular genotype
53
What is variable expressivity?
The degree of severity in an individual who inherits a disease causing mutation
54
What is a phenocopy?
Disease with the same phenotype as a genetic disease, but non-genetic eg Autoimmune haemophilia
55
What is epistasis?
Interaction between disease gene mutations and other modifier genes can affect phenotype
56
What is consanguinity?
Two individuals are related
57
What is genetic imprinting? Give two examples.
Where genes are expressed differently according to whether they are inherited from the mother or the father. Paternal- Prader-Willi Maternal- Angelman Occurring on the same chromosomal region on Chr15
58
What is Ovarian Teratoma?
Where the genome of a child has only come from the mother
59
What is Hydatidiform Mole?
Where the genome of a child has only come from the father
60
What non-genetic factor can lead to congenital abnormalities?
Mitochondrial disorders (inheritance)
61
What is a mitochondrial disorder? Who does it affect, how is it transmitted? Give two examples.
Distinct inheritance pattern. Transmission through females. Affects both males and females. Only certain cells will be affected as mitochondria are present in different numbers in different cells e.g. MELAS (Mitochondrial myopathy, Encephalopathy, Lactic acidosis and Stroke)- progressive neurodegenerative disorder LHON (Leber's Hereditary Optic Neuropathy)- More common in males? Blindness
62
What does the UK newborn screening programme screen for?
``` PKU (PhenylKetonUria) Congenital hypothyroidism Sickle cell disorders Cystic fibrosis MCAD Deficiency (Medium-Chain Acyl-coA Dehydrogenase) ```
63
What is a somatic mutation?
Alterations in DNA that occur after conception. Occurs in any of the body cells except the germ cells so is not passed on to children
64
What is a germline mutation?
Any detectable and heritable variation in the lineage of germ cells. Mutations are transmitted to offspring.
65
What is an oncogene? Where do they arise?
An oncogene is a gene that causes cancer. It arises from the mutation of a normal gene (proto-oncogene). It produces proteins (e.g. growth factors, transcription factors, tyrosine kinases) that transform a normal cell into a malignant cell.
66
How does a tumour suppressor gene cause cancer?
Downregulation of tumour suppressor genes can cause cancer. Most TS genes require two mutations for tumorigenic effect. Hit 1 and hit 2 cause loss of transcription to cause a malignant phenotype. Some genes require only 1 hit
67
What genes are responsible for an inherited predisposition to breast and ovarian cancer?
BRCA1 and BRCA2 (60% risk of inheriting cancer)
68
What is the genetic mechanism for the increased risk of cancer associated with BRCA1 and BRCA2?
BRCA1 and BRCA2 repair double strand breaks in cooperation with Rad15, called homologous recombination. Point mutations, several base pair deletions, whole exon deletions and amplifications of the BRCA1/2 gene are associated with increased risk of cancer as they result in a truncated non-functional protein
69
What genes are associated with an increased risk of colorectal cancer?
FAP and HNPCC
70
How is FAP responsible for increased risk of bowel cancer?
FAP (familial adenomatous polyposis) is the growth of thousands of intestinal polyps, one or more of which is likely to become cancerous. Virtually 100% risk of cancer
71
What is HNPCC?
HNPCC (hereditary non-polyposis colorectal cancer) is commonly a mutation in MLH1 and MLH2 repair genes
72
What is MYH polyposis?
A less common bowel cancer syndrome. It is autosomal recessive characterised by two mutated alleles of the MYH gene (mutY Homologous/MUTYH)
73
What chromosome translocation is associated with chronic myeloid leukaemia?
Blood cells in patients contain a reciprocal translocation between chromosome 9 and 22, which leads to a foreshortened long arm of chromosome 22
74
What treatment is used for chronic myeloid leukaemia?
Imatinib- a tyrosine kinase inhibitor (20-30% of patients are immune to Imatinib)
75
Why is cytogenetics important?
i.e. quantify outstanding disease Defines response to treatment and helps clinical management, absence of cytogenetic response after 12 months indicates change of therapy, change in cytogenetics predictive of survival, loss of major molecular resistance indicator of therapy resistance and imminent relapse.
76
What is a pharmacogenomic marker? Give 3 examples.
Is the drug response based on genetic influences, showing the effects of genes on drug response e.g. p53- deletions in chronic lymphocytic leukaemia and multiple myeloma predict for aggressive disease and may change patient management (FISH) HER2 (ERB2) amplification in breast cancer is a marker of aggressive disease but also predicts efficacy of herceptin (FISH) T315I mutation in chronic myeloid leukaemia predicts resistance to tyrosine kinase inhibitor therapy (direct sequencing)
77
What is G-banding?
A technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes. Metaphase chromosomes are treated with trypsin and stained with Giemsa. Dark strands that take up the stain are A and T rich. Useful to identify differences between chromosomes
78
When are routine ultrasound scans conducted during pregnancy?
11-14 weeks (Nuchal scan) and 20-22 weeks
79
What is nuchal translucency? What does it screen for?
Increased thickness of fluid at the back of foetal neck. Indicates increased risk of genetic syndromes such as Down, Edwards, Patau, Turners
80
What indications would require referral to Genetic Services regarding prenatal testing?
Abnormal findings at nuchal scan or mid-trimester scan, results of combined test which give increased risk of Down syndrome, previous pregnancy affected with condition (cystic fibrosis or down syndrome) or if parents are a carrier of chromosome rearrangement or genetic condition
81
What is ultrasound used for in pregnancy?
Early/dating scan, nuchal translucency and nasal bone, high-level anomaly scan
82
When is a foetal MRI scan used in pregnancy?
Usually around 20 weeks onwards
83
What is HCG?
Human Chorionic Gonadotrophin- The main pregnancy hormone. It is made in the placenta and acts to maintain a pregnancy
84
What biochemical markers would you expect to see in a maternal blood test during pregnancy? (4)
``` Foetal AFP (α-foetalprotein) (leaks into maternal blood) HCG (human chorionic gonadotrophin) (major pregnancy hormone) E3 (breakdown product of active oestrogen) PAPP (Pregnancy-associated plasma protein) ```
85
What are the two types of minimally invasive testing conducted during pregnancy?
Maternal blood test | Cell-free DNA
86
What are the two types of invasive testing conducted during pregnancy?
Chorionic villus sampling (CVS) | Amniocentesis
87
In the first trimester what biochemical markers are measured in maternal serum testing?
hCG | PAPP
88
In the second trimester what biochemical markers are measured in maternal serum testing?
AFP uE3 hCG
89
What is cfDNA testing? When is it performed?
Cell-free DNA testing tests the foetal DNA circulating in the mother's blood. It is not accurately detected until 9 weeks into the pregnancy and is cleared within the first hour following birth
90
How is cfDNA testing used to sex the pregnancy?
Tests the SRY gene on the Y chromosome
91
What is CVS testing? When is it conducted? What are the risks?
Chorionic Villus Sampling is conducted at 11-14 weeks. It is transabdominal or transvaginal. There is a 1-2% chance of miscarriage. It takes part of the chorionic villi, part of the developing placenta which has the same DNA as the foetus. Allows patients to get results earlier than amniocentesis
92
What is Amniocentesis? When is it conducted? What are the risks?
Conducted from 16 weeks onwards. It takes a sample of the amniotic fluid which contains foetal cells. Up to 1% risk of miscarriage. Needle passed through the abdomen and amniotic fluid is aspirated.
93
What are the reproductive options available to couples? (6)
``` Conceive naturally, no prenatal testing Conceive naturally, have prenatal testing Use of egg/sperm donors Adoption Choose not to have children Pre-implantation genetic diagnosis (PGD) ```
94
What is PGD?
Pre-implantation genetic diagnosis | IVF with an additional step to genetically test the embryo before implantation
95
What is IVF
In-vitro fertilisation | Sperm and egg placed together in a culture dish
96
What is ICSI
Intra-cytoplasmic sperm injection | Injection of a single sperm into each egg
97
How can we estimate the heritability of a common complex disease?
Twin studies of monozygotic and dizygotic (identicle and fraternal) twins
98
What is the most common single-gene cause of obesity?
MC4R
99
How does the leptin-melanocortin pathway contribute to obesity?
Causes leptin deficiency which leads to hunger, obesity, no puberty, poor growth, low thyroid and immune problems

MCD Year 1 (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions