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Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceBIOLOGYPrinciples of Inheritance and Variation4 Marks
Question
Explain any two X-linked recessive disorder?
✓

Answer

X-Linked recessive disorder:
→ (i) colourblindness, (ii) Haemophilia.
→ (i) Colour Blindness:
→ It is a sex-linked recessive disorder due to defect in either red or green cone of eye resulting in failure do discriminate between red and green colour.
→ This defect is due to mutation in certain genes present in the X-chromosomes.
→ It occurs in about 8 per cent of males and only about 0.4 per cent of females.
→ This is because the genes that lead to red-green colour blindness are on the X-chromosomes. Males have only one X-chromosomes and females have two.
→ The son of a woman who carries the gene has a 50 per cent chance of being colour blind.
→ The mother is not herself colour blind because the gene is recessive. That means that its effect is suppressed by her matching dominant normal
gene.
→ A daughter will not normally be colour blind, unless her mother is a carrier and her father is colour blind.
→ (ii) Haemophilia:
→ This sex linked recessive disease, which shows its transmission from unaffected carrier female to some of the male progeny has been widely studied.
→ In this disease, a single protein that is a part of the cascade of proteins involved in the clotting of blood is affected.
→ Due to this, in an affected individual a simple cut will result in non-stop bleeding.
→ The heterozygous female (carrier) haemophilia may transmit the disease to sons.
→ The possibility of a female becoming a haemophilic is extremely rare because mother of such a female has to be at least a carrier and the father should be haemophilic (unviable in the later stage of life.)
→ The family pedigree of Queen Victoria shows a number of haemophilic descendents as she was a carrier of the disease.

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Reerna, Jai and Ankit are suffering from autoimmune diseases of adrenal cortex, joints and thyroid gland, respectively. Their immune system failed to recognise self and non-self and started destroying their body's own proteins. They are seeking proper medical help for their conditions but their condition cannot be cured completely.

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S no.
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Jai
Ankit
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  2. To supply oxygen to the cells of the anther.
  3. To transport food and mineral salts to the anther.
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  3. A, B and D only.
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S. No
Structure of X
Stamens
(a)
Abundant and light
Pendulous
(b)
Rough surfaces
Non-pendulous
(c)
Light and sticky
Pendulous
(d)
Coarse and sticky
Protrude outside the flower
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The process of copying genetic information from template strand of DNA into RNA is called transcription. It is mediated by RNA polymerase. Transcription takes place in the nucleus of eukaryotic cells. In transcription, only a segment of DNA and only one of the strands is copied into RNA.

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  1. Poly-A polymerase
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Reason: Prokaryotic RNA polymerase has sigma $(\sigma)$ factor.

  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
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  3. DNA template.
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  1. (1) (2) (3) and(4)
  2. (1) (2) (3) (5) and(6)
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During copulation, semen is released by the penis into the vagina. 'The motile sperms swim rapidly, fuse with ovum in the ampullary region, resulting in fertilisation. Haploid nucleus of sperm fuse with that of ovum to form diploid zygote.

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  2. Cortical reaction.
  3. Capacitation.
  4. Acrosomal reaction.
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  1. Fusion of cortical granules with plasma membrane of secondary oocyte.
  2. Formation of fertilisation cone to receive sperm.
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  1. R → Q → P → S
  2. Q → S → R → P
  3. Q → R → S → P
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  3. It initiates cleavage.
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  1. Most commonly used matrix is _____ which is a ______ extracted from _______.
  1. (i) agarose (ii) polysaccharide (iii) sea weed
  2. (i) agarose (ii) protein (iii) sea weed
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  1. (iii) → (ii) → (i)
  2. (i) → (ii) → (iii)
  3. (i) → (iii) → (ii)
  4. (iii) → (i) → (ii)
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  2. DNA fragments are separated according to their size.
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  4. None of these.
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During teaching about various environmental factors, a teacher draw a figure that depicts like history strategies for three plant species (X, Y and Z) along 3 axes - strength of competition with other organisms, level of disturbance in the habitat and level of environmental stress in the habitat. Species X grows in habitats where competition among species is high but disturbance and stress are low. Species Y grows in habitats with high environmental stress but with low intraspecies competition. Species Z grows in highly disturbed habitats with low environmental stress.

  1. Which of the following is correct regarding plant type X?
  1. It has slow growth rate.
  2. It lives in area with high probability of severe environmental changes.
  3. It has good competitive ability at low population densities near the carrying capacity.
  4. None of these.
  1. Environmental stress occurs through.
  1. Very low temperature.
  2. Drought.
  3. Nutrient deficiency.
  4. All of these.
  1. Select the correct option regarding plant type X, Y and Z.
  1. X type of plants are likely to be trees.
  2. Y type of plants could be desert plants.
  3. Z type of plants could be herbaceous plant.
  4. All of these.
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  1. Produce large number of seeds in a short time after rains.
  2. Have rapid growth.
  3. Produce less number of seed in a long time after rain.
  4. Both (a) and (b).
  1. Assertion: Plant growth rate is high in area of high stress and high disturbance.

Reason: High stress and high disturbance promote breeding capacity in plants.

  1. Both assertion and reason are true and reason is the correct explanation of assertion.
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Growth of a population with time shows specific and predictable patterns. Two types of growth pattern of population are exponential and logistic growth. When resources in the habitat are unlimited each species has the ability to realise fully its innate potential to grow in number. Then the population grows in exponential fashion. When the resources are limited growth curve shows an initial slow rate and then it accelerates and finally slows giving the growth curve which is sigmoid.

  1. Which of the following statement is incorrect?
  1. Exponential growth occurs in organism such as lemmings.
  2. Logistic growth is more realistic.
  3. Exponential growth has two phases lag and log.
  4. ln logistic growth, population passes well beyond the carrying capacity of ecosystem.
  1. Which of the following equations correctly represents the exponential population growth curve?
  1. $\text{dN}/\text{dt}=\text{rN}$

  2. $\text{dN}/\text{dt}=\text{rN}\Big(\frac{\text{K-N}}{\text{K}}\Big)$

  3. $\text{N}_\text{t}=\text{N}_\text{o}\text{e}^\text{rt}$

  4. Both (a) and (c).
  1. Which of the following equations correctly represents Verhulst-Pearl logistic growth?
  1. $\text{dN}/\text{dt}=\text{rN}\Big(\frac{\text{K-N}}{\text{K}}\Big)$

  2. $\text{dN}/\text{dt}=\frac{\text{rN}}{\text{K}}$

  3. $\text{dN}/\text{dt}=\frac{\text{N}(\text{K}-\text{N})}{\text{K}}$

  4. $\text{dN}/\text{dt}=\frac{\text{r}(\text{K}-\text{N})}{\text{K}}$

  1. The population growth is generally described by the following equation:

$\frac{\text{dN}}{\text{dt}}=\text{rN}\Big(\frac{\text{K}-\text{N}}{\text{K}}\Big)$

What does 'r' represent in the given equation?

  1. Population density at time 't'.
  2. Intrinsic rate of natural increase.
  3. Carrying capacity.
  4. The base of natural logarithm.
  1. Study the population growth curves (A and B) in the given graph and select the incorrect option.

  1. Curve 'A: shows exponential growth, represented by equation $\frac{\text{dN}}{\text{dt}}=\text{rN}$.

  2. Curve 'B' shows logistic growth, represented by equation $\frac{\text{dN}}{\text{dt}}=\text{rN}\Big(\frac{\text{K}-\text{N}}{\text{K}}\Big)$

  3. Exponential growth curve is considered as more realistic than the logistic growth curve.
  4. Curve 'A' can also be represented by equation $\text{N}_\text{t}=\text{N}_\text{o}\text{e}^\text{rt}$.

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The anther is a four-sided structure consisting of four microsporangia located at the corners, two in each lobe. TI1e microsporangia develop further and become pollen sacs. In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers-the epidermis, endothecium, middle layers and the tapetum.

  1. A dithecous another consists of (A) microsporangia, (B) in each lobe.

Select the option that correctly fills the blanks.

S. No
A
B
(a)
Four
Two
(b)
Two
One
(c)
Two
Two
(d)
Four
One
  1. The given diagram shows microsporangium of a mature anther. Identify A, B and C.

(a)
A-Middle layer
B-Endothecium
C-Tapetum
(b)
A-Endothecium
B-Tapetum
C- Middle layer
(c)
A-Endothecium
B-Middle layer
C-Tapetum
(d)
A-Tapetum
B-Middle layer
C-Endothecium
  1. The function of labelled part X is:

  1. Dehiscence.
  2. Mechanical.
  3. Nutrition.
  4. Protection.
  1. Select the incorrect statement.
  1. Microsporangium is generally surrounded by four wall layers-epidermis, endothecium, middle layers and tapetum.
  2. Outer three layers perform functions of protection and dehiscence of anthers.
  3. Cells of tapetum possess dense cytoplasm and generally have more than one nucleus.
  4. Cells of tapetum undergo meiosis and produce microspore tetrads.
  1. Which function oftapetum is correct?
  1. Helps in pollen wall formation.
  2. Transportation of nutrients to inner side of another.
  3. Synthesis of callase enzyme for separation of microspore tetrads.
  4. All of these.
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