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Human Biology Unit 2 - Semester 2 > Chapter 22 - Inheritence > Flashcards

Chapter 22 - Inheritence Flashcards

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1
Q

What were the two principles relating to inheritance put forward by Austrian Monk Gregor Mendel?

A
  1. The various hereditary characteristics were controlled by factors (one called GENES) and that these occurred in pairs.
  2. During the formation of the Gametes (in humans, the eggs and the sperm), the pair of factors separate.
    • each gamete Receives only one set of factors or genes, the other set going to the other gamete.
    • Gametes unite at fertilisation, allowing different combinations of genes to come together.
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2
Q

What are genes?

A

A segment of DNA located in a chromosome containing information for a specific trait.

Genes can also suppress and enhance these traits it’s responsible for.
(Acetylation and methylation)

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3
Q

What is Cytology?

A

Cytology is a feild in biology - the study of cells.

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4
Q

Mendel - Walter Sutton

A

Walter Sutton (young American graduate student) linked the work of Mendel to that of the cytologists.

His observations of the behaviour of chromosomes during meiosis and speculation of Mendel’s speculation on the separation of the hereditary factors during the formation of Gametes.
- led Sutton to suggest
HEREDITARY FACTORS, OR GENES, WERE LOCATED IN THE CHROMOSOMES.

  • this important hypothesis contained in a research paper he published in 1903, led to the CHROMOSOME THEORY OF HEREDITARY.
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5
Q

List some dominant human traits

A
  1. Free earlobes
  2. Broad lips
  3. Long eyelashes
  4. Broad nostrils
  5. Abundant body hair
  6. Curly hair
  7. Mongolian eye fold
  8. Astigmatism
  9. Roman nose
  10. Huntington’s disease
  11. Achondroplasia
  12. Normal enzyme production
  13. Normal pigmentation
  14. Tongue rolling
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6
Q

What are some recessive traits in humans

A
  1. Attacked earlobes
  2. Thin lips
  3. Short eyelashes
  4. Narrow nostrils
  5. Little body hair
  6. Straight hair
  7. No eye fold
  8. Normal vision
  9. Straight nose
  10. No disorder
  11. Normal build
  12. Phenylketonuria
  13. Albinism
  14. Non rolling tongue
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7
Q

Define Allele

A

An alternative form of a gene

  • an individually normally has one or 2 alleles for each gene
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8
Q

Homozygous Vs Heterozygous

A

Homozygous: the situation where an individual has the same alleles for a particular characteristic- pure breeding

Heterozygous: the situation where an individual posses different alleles for a particular trait - hybrid

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9
Q

What is a Cross vs. Monohybrid Cross

A

A cross is the mating of 2 organisms

In A monohybrid Cross only one pair of contrasting characteristics is studied.

  • a cross between two organisms with different variations at one genetic chromosome of interest
  • this cross is governed by two or multiple variations for a single locus.
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10
Q

Explain Mendel’s discoveries

A
  1. Mendel conducted breeding experiments with the edible garden pea ‘Pisum’
    * was impressed by the fact that it possess a number of characteristics/traits that were expressed in contrasting forms.
    * studied 7 pairs of contrasting in which alternatives were easily identifiable
  2. Using Pure-bred pea plants he crossed/interbred these purebred plants with contrasting traits.
  3. The progeny produced where hybrids because they genetic information from both parent plants.
    - the trait showed by the hybrid plant - dominant
    - the trait appearance masked by the hybrid - recessive
  4. Then he allowed the hybrid plants to self-pollinate creating a second generation of plants were produced.
    - 3:1 ratio (dominant : recessive) was shown by this generation
  5. From these results he concluded that the hereditary factors/genes were unchanged as they passed from one generation to the next.
  6. Further reasoned that each pea plant had 2 hereditary factors for each characteristic under his study, and called it the PRINCIPLE OF SEGREGATION
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11
Q

Explain the principle of segregation

A

During the formation of Gametes, genes (factors) are separated or SEGREGATED - Each gamete receiving only one factor or gene for each trait.

As offspring are formed by the union of male and female gamete - each offspring recurved one gene for each characteristic from each parent.

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12
Q

Define progeny

A

The offspring

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13
Q

What is pure breeding?

A

Pure breeding are those individuals that produce the same characteristic for a particular trait.

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14
Q

First filial generation vs second filial generation

A

First - denoted by F(1)
Second - denoted by F(2)

The F1 (first filial) generation consists of all the offspring from the parents.

The F2 (second filial) generation consists of the offspring from allowing the F1 individuals to interbreed

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15
Q

What are punnet squares?

A

square diagram that is used to predict the genotypes of a particular cross or breeding experiment.

R.C. Punnet, a British geneticist

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16
Q

What are the 5 complete dominance/recessive related diseases in humans? Autosomal

A
  1. Huntington’s Disease (Dominant)
  2. Phenylketonuria (recessive)
  3. Thalassaemia (recessive)
  4. Cystic fibrosis (recessive)
  5. Tay - Sachs disease (recessive)
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17
Q

Explain Huntington’s Disease

A

In humans Huntington’s disease is CONTROLLED BY A DOMINANT GENE ALLELE
- mutated on chromosome 4. Mutated protein - huntingtin

Passed down from ONE GENERATION TO the NEXT.

SYMPTOMS: appear in life approximately after 30-40yrs age
Affects - part of brain (nerve cells) that controls movement.
Results in uncontrollable jerky movements, involuntary flailing of arms and legs, rigidity-ness of body, affects speech, ability to think and swallow, dementia - memory loss

No cure - treatment can either slow progression/reduce magnitude of symptoms

Need one ALLELE ONLY - Coz completely dominant
Uncommon 1:20 000

18
Q

Explain Phenylketonuria

A

PKU is a rare disease controlled by a RECESSIVE ALLELE.e

Caused by mutated gene on chromosome 12 for the enzyme that breaks down phenylalanine to tyrosine.

This means the body cannot break down this Amino Acid and therefore build up of toxic phenylalanine causing
- mental retardation

Treatment: controlled diet - low levels of this protein phenylalanine found in milk, eggs and meat

Need 2 recessive allles - recessive
- OFTEN SKIPS A GENERATION

Tested after birth via Heel prick test

1:50 000

19
Q

Examples of Co -Dominance not in humans

A
  1. Speckled Chook - Black chicken (B) and White Chicken (W) genotype results (BW) a speckled chicken (not grey!)
  2. Roan Coloured Cattle - red and white colour genes (RW) makes the cows coat have red and white hairs
20
Q

Explain Examples of Co-Dominance in Humans

A
  1. ABO blood group (I^(A) or (B) or (AB) or (O)

2. Sickled cell anemia

21
Q

Explain Sickled Cell anemia

A

In sickled cell anaemia (inherited by people of black African ancestry 40%)

It results in the red blood cells being in a crescent-like or sickled shape.

If homozygous- the disease is fatal as the sickled RBCs do not carry as much oxygen as normal, they can stick together and block small blood vessels.
- sometimes death
Heterozygous individuals are carriers and suffer from Sickle -cell trait.
(Co-dominant) The sickle cell trait gauges certain advantages to those who have it; provides a a degree of immunity to malaria (a disease that is found where sickle celled gene are prevalent)

22
Q

Define Multiple Alleles

A

There are more than 2 alleles for a particular characteristic.

The position of that gene on a chromosome is called multi-allelic

23
Q

What is polymorphism?

A

Polymorphism is where many different physical forms can result from the various alleles at a single gene location.

Situations where multiple alleles are involved are referred to as polymorphic

24
Q

What is a Carrier?

A

People who carry a recessive but do not show the recessive phenotype are known as carriers.

25
Q

Explain the ABO blood grouping system

A

A system, the classification of human blood based on the inherited properties of red blood cells.

determined by the presence or absence of the antigens A and B, which are carried on the surface of the red cells.

26
Q

What is Incomplete Dominance?

A

The result of heterozygous genotype’s phenotype is a Blend.

27
Q

Example of incomplete dominance?

A

4 O’ clock flowers (Mirabilis Jalapa)
- red and white flowers blended to have pink petals

Eg. 2 heterozygous pink crossed ratio

  • 1/4 red
  • 1/2 pink
  • 1/4 white
28
Q

What are Autosomes? What are sex chromosomes?

A

The pair of chromosomes that regulate the somatic characters of the body are known as autosomes, whereas the pair of chromosomes that determines the sex of an organism, as they regulate the sex-linked traits are known as sex chromosomes or allosomes.

29
Q

List the Sex linked disorders

A
  1. Haemophilia
  2. Red/Green Colour Blindness
  3. Duchenne Muscular Dystrophy
  4. Diabetes Insipidus
30
Q

Define Hemizygous

A

Hemizygous is a condition in which only one copy of a gene or DNA sequence is present in diploid cells.

Males are hemizygous for most genes on sex chromosomes, having only one X and one Y chromosome.

31
Q

What are sex linked Characteristics?

A

Or X-linked characteristics

Characteristics that show different patterns in the 2 sexes.

Eg. Red/green colourblindness and Haemophilia

32
Q

Explain why Sex- linked characteristics occur

A

Y chromosome has less genes
X - chromosomes will lack matching alleles in males and therefore males are more affected than females.

Genes are located on the X chromosomes

Symbol - X (with subscript) and Y (no subscript)

33
Q

Explain Red green Colour Blindness

A

Ability to discriminate between the colours red and green is controlled by a gene located in the X chromosome.

Individuals who are unable to distinguish between the two colours posses the recessive allele of the gene.

As the gene is located in the X chromosome, this form of colour blindness is found more frequently in males than females.

34
Q

Explain Haemophilia

A

Is a recessive rare disease in which blood clots slowly or not at all.

The defective allele is recessive to that controlling normal clotting if the blood and is carried on the X chromosome.

Makes the fire can be either normal or haemophiliacs, as they have only one X chromosome.

35
Q

Explain the pattern of inheritance of Haemophilia

A

Haemophiliac fathers pass the recessive gene to their daughters

Carrier mother’s may pass defective gene to their son’s who will be haemophiliacs, and the daughters can be carriers if passed down.

36
Q

Explain Diabetes Insipidus

A

A sex linked disorder in which the affected individual passes very large quantities of urine and gradually becomes dehydrated.

Kidneys are unable to concentrate urine.

Death may result unless water is available to replace lost amount.

37
Q

Explain Duchenne Muscular Dystrophy

A

The Duchenne form of muscular dystrophy is a wasting disease of leg muscles, later arms, shoulders and chest.

At times may be due to mutation - either in a woman making her a carrier or in a boy giving him the disease.

Become apparent at ages 3-5 when muscles weakness becomes evident.

As years pass more muscle tissue wastes away and is replaced by fatty substances.

By age 12-14 the child is confined in a wheelchair and later bedridden.

With respiratory failure, death becomes inevitable.

Little chance of living over 20-25 years of age.

38
Q

What is Mitochondrial DNA? mtDNA

A

DNA found in the Mitochondrion

We inherit nuclear DNA from both parents via fertilisation, however only mitochondrial DNA from the mother because the middle piece of the sperm gets destroyed after fertilisation.

Determines our metabolism rates.

39
Q

What is genetic disease ?

A

An inherited medical condition caused by a DNA abnormality.

Having marriages between cousins or relatives cause genetic disorders to be common in particular groups as they a common ancestor and gene locus - making chances increase

40
Q

What are some genetic diseases within a population?

A
  1. Thalassaemia
  2. Sickled cell anaemia
  3. Tay -Sachs disease
41
Q

Explain Thalassaemia

A

Recessive disease found near Mediterranean Sea.(italian, greece)

Anaemia results from defects in the formation of haemoglobin, is relatively high

People with thalassaemia require frequent blood transfusions throughput their life and special drugs to remove excess iron that tends to build up in the body.

42
Q

Explain Tay- Sachs disease

A

Autosomal recessive hereditary disorder

Fatal disorder caused by a missing enzyme that results in the acculturation of fatty substance in nervous system

Eg, a baby who has tay-Sachs develops Normally for the first few months, but then deterioration causing mental and physical disabilities to begin.

Death in early childhood.

Occurs in Ashkenazi Jews population

Human Biology Unit 2 - Semester 2 (12 decks)

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