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Higher Biology > 2.4 > Flashcards

2.4 Flashcards

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1
Q

What is the goal of antenatal screening?

A

aims to detect abnormalities in the foetus and pregnancy and assess risk of developing certain disorders.

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2
Q

What is the role of a dating scan?

A

to determine the stage of the pregnancy and to estimate the due date. Tests for chemical markers of pregnancy are also perfomed at the dating scan.

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3
Q

What is the role of an anomaly scan?

A

to detect potential serious physical abnormalities in the foetus.

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4
Q

Why are blood and urine tests carried out throughout pregnancy?

A

to monitor the concentrations of pregnancy marker chemicals.

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5
Q

What is amniocentesis?

A

an antenatal screening technique which involves collecting a sample of amniotic flud from the amniotic sac for analysis of genetic disorders.

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6
Q

What are the advantages of amniocentesis?

A
  • prenatal diagnosis possible
  • detects neural tube defect
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7
Q

What are the disadvantages of amniocentesis?

A
  • small risk of a miscarriage
  • gives results later in the pregnancy
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8
Q

What is chorionic villus sampling (CVS)?

A

an antenatal screening procedure that involves collecting a sample of cells from the placenta for analysis of genetic disorders.

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9
Q

What is an advantage of CVS?

A

it can be carried out as early as 8 weeks and therefore allowing the information to gathered earlier

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10
Q

What is an disadvantage of CVS?

A

CVS causes a higher incidence of miscarriage than amniocentesis.

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11
Q

Give three difference between amniocentesis and CVS

A
  1. amniocentesis is carried out between 14-16 weeks, whereas CVS can be performed at 8 weeks.
  2. amniocentesis involves collecting amniotic fluid, whereas CVS involves collecting cells from the placenta.
  3. the results from amniocentesis take a couple of weeks to come back, however CVS allows for immediate karyotyping.
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12
Q

What is the main risk involved in performing amniocentesis and CVS?

A

there is a risk of miscarriage for both amniocentesis and CVS risk is slightly higher in CVS.

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13
Q

What is involved in genetic counselling?

A

involves investigating, discussing and treating possible genetically-linked medical conditions that may affect an individual or their famiy.

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14
Q

What is a dominant allele?

A

produces its associated phenotype whether its paired allele is the same or different.

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15
Q

What is a recessive allele?

A

produces its associated phenotype only when its paired with the same recessive allele.

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16
Q

Describe the term “homozygous”

A

a cell that has inherited two identical alleles of the same gene

17
Q

Describe the term “heterozygous”

A

a cell that has inherited two different alleles of the same gene

18
Q

Describe what happens in incomplete dominance inheritance patterns

A

This occurs when neither allele is dominant over the other for a gene. When both appear in the genotype, the phenotype is a mixed picture of the two.

19
Q

What is an example of autosomal incomplete dominance?

A

Sickle cell anaemia (fully expressed) and sickle-cell trait (partly expressed)

20
Q

What are the characteristics associated with autosomal incomplete dominance?

A
  • the fully expressed form of the charcateristic occurs relatively rarely
  • the partly expressed form occurs much more frequently
  • males and females are affected in approximately equal numbers
21
Q

What is the genotype of the fully expressed form (sickle-cell anaemia) of the characteristics - autosomal incomplete dominance

A

homozygous for the other incomplete dominant allele
SS

22
Q

What is the genotype of the partly expressed form (sickle-cell trait) of the charcteristics - autosomal incomplete dominance

A

heterozygous for the two alleles
HS

23
Q

What is the genotype of someone without the characteristics - autosomal incomplete dominance

A

homozygous for one incomplete dominant allele
HH

24
Q

What is a sex-linked gene?

A

a gene that appears on the portion of the X chromosome that is absent from the Y chromosome.

25
Q

What is an example of sex-linked recessive trait?

A

Haemophilia

26
Q

What is the characteristics associated with sex-linked recessive trait?

A
  • many more males have the trait than females
  • none of the sons of a male with the trait show the trait
  • some of the grandsons of a male with the trait do show the trait
27
Q

What is the genotype of someone with the trait - sex-linked recessive trait

A

homozygous recessive
male - X^hY female - X^hX^h

28
Q

What is the genotype of someone without the trait - sex-linked recessive trait

A

homozygous dominant
male - X^HY female - X^HX

heterozygous carrier females
X^HX^h

29
Q

Why do sex-linked recessive gene affect males more than females?

A

As females have two X chromosomes, she would need two recessive alleles to express the recessive trait in her phenotype.

Males have only one X chromosomes so they need only one recessive allele to express the recessive trait in his pheotype.

30
Q

What is an example of autosomal recessive inheritance?

A

Cystic Fibrosis (CF)

31
Q

What are the characteristics of autosomal recessive inheritance?

A
  • the trait is expresed relatively rarely
  • the trait may skip generations
  • males and females are affected in approximately equal numbers
32
Q

What is the genotype of someone who had the trait - autosomal recessive

A

homozygous recessive
cc

33
Q

What is the genotype of someone without the trait - autosomal recessive

A

homozygous dominant
CC
heterozygous (carrier)
Cc

34
Q

What is an example of autosomal dominant inheritance?

A

Huntington’s Chorea

35
Q

What are the characteristics associated with autosomal dominant inheritance?

A
  • the trait appears in every generation
  • each person with the trait has an affected
    parent
  • males and females are affected in approximately equal numbers
36
Q

What is the genotype of someone with the trait - autosomal dominant

A

homozygous dominant or heterozygous
CC or Cc

37
Q

What is the genotyped of someone without the trait - autosomal dominant

A

homozygous recessive
cc

Higher Biology (24 decks)

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