cells and control sample questions and answers Flashcards

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1
Q

How many pairs of chromosomes are present in a diploid nerve cell?

A

23

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2
Q

What happens immediately before mitosis in the cell cycle?

A

Checking for errors in copied DNA

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3
Q

What phase in mitosis involves the pulling of chromosomes and their copies to different ends of the cell?

A

Anaphase

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4
Q

Explain the difference between sensory, relay and motor neurones in terms of the direction that their electrical signals travel. [3 marks]

A
  • sensory neurones carry electrical signals from receptors to the central nervous system
  • relay neurones carry electrical signals within the central nervous system (brain and spinal cord)
  • motor neurones carry electrical signals away from the central nervous system to effectors (muscles and glands)
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5
Q

Explain why reflex arc signals do not immediately go to the brain. [2 marks]

A
  • because it would take longer to react if they did

- this might increase any damage to the body

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6
Q

Describe how are embryonic and adult stem cells different? [2 marks]

A
  • adult stem cells are only found in specific locations like the nose and bone marrow
  • embryonic stem cells make up all of an embryo
  • adult stem cells can only differentiate into a small number of cell types
  • embryonic stem cells can differentiate into all cell types
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7
Q

State what types of human cells are not produced by mitosis? [1 marks]

A

Gametes (sperm and ova)

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8
Q

Describe how someone with short sight can see more clearly? [3 marks]

A
  • they can wear concave lenses in glasses

- they could also wear contact lenses or undergo laser surgery

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9
Q

Explain the process of accommodation. [4 marks]

A

Answer (four from):

  • to focus on a near object, the lens becomes thicker
  • thicker lens allows the light rays to refract (bend) more strongly
  • thicker lens allows light to focus on the retina
  • to focus on a distant object, the lens is pulled thin
  • thinner lens this allows the light rays to refract slightly
  • thinner lens allows light to focus on the retina
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10
Q

A baby boy is born in the 9th percentile for height. Explain what this means for him in terms of the rest of the population. [1 mark]

A

For every 100 boys, 91 will be taller than him and only 8 will be shorter.

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11
Q

Describe the method used to investigate the speed of reaction times. [4 marks]

A

Answer (four from):

  • person A holds out their hand with a gap between their thumb and first finger
  • person B holds the ruler with the zero at the top of person A’s thumb
  • person B drops the ruler without telling Person A and they must catch it
  • the number level with the top of person A’s thumb is recorded in a suitable table - repeat this ten times
  • swap places, and record another ten attempts
  • you can use the conversion table to help convert your ruler measurements into reaction time or just record the catch distance in cm
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12
Q

Describe how you could adjust this method to show the effect of stimulants in reaction times. [2 marks]

A

Answer (two from):

  • both person A and B both drink a caffeinated drink after they have measured their reaction times
  • wait fifteen minutes for the caffeine to have an effect on the nervous system
  • repeat the experiment and compare the results
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13
Q

Describe the structure and function of the nerves in the nervous system. [6 marks]

A
  • the central nervous system is made up of the brain and spinal cord
  • the peripheral nervous system is a network of nerves that cover the rest of the body
  • receptor cells in sense organs start electrical signals which travel along sensory neurones to the central nervous system (two marks)
  • relay neurones carry electrical signals around the central nervous system
  • motor neurones carry electrical signals away from the central nervous system to effectors which are muscles or glands (two marks)
  • gaps between neurones are called synapses
  • all neurones have extended projects called axons along which electrical signals travel
  • axons are insulated by myelin sheaths to speed up the electrical signals
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14
Q

Describe the structure of DNA in a eukaryotic cell. [6 marks]

A
  • DNA is made of four base pairs
  • A-T, T-A, C-G, G-C
  • bases are joined together by weak hydrogen bonds
  • DNA is coiled into a double helix shape
  • a section of DNA that codes for a protein is called a gene
  • genes come in pairs called alleles
  • chromosomes are long lengths of DNA which contain many genes
  • an organism’s entire DNA is called a genome
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15
Q

Describe the steps in mitosis. Give their names in your answer. [6 marks]

A
  • interphase - the DNA in chromosomes copies itself ready for mitosis
  • prophase - the membrane around the nucleus disappears
  • metaphase - chromosomes and their copies line up in the middle of the cell
  • anaphase - chromosomes and their copies are pulled to different ends of the cell
  • telophase - new membranes form around the chromosomes at each end of the cell
  • cytokinesis - the cell membrane pinches in and eventually divides into two daughter cells
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16
Q

Describe the differences in the cells produced in mitosis and meiosis. [4 marks]

A
  • mitosis produces two [1 mark] identical [1 mark] diploid [1 mark] daughter cells
  • meiosis produces four [1 mark] non-identical [1 mark] haploid [1 mark] daughter cells
17
Q

Explain how and where cell differentiation in plants occurs. [4 marks]

A

Answer (four from):

  • mitosis in plant cells occurs in the meristems
  • these are areas in the tips of roots and shoots
  • mitosis produces stem cells in meristems
  • these can differentiate into any type of cell
  • as the root or shoot grows further stem cells are produced
  • older stem cells differentiate to become part of the shoot or root
  • this means they become larger [1 mark] and form permanent vacuoles [1 mark]
18
Q

Describe how mutations in DNA are caused and explain their possible effects. [5 marks]

A

Answer (five from):

  • mutations are changes in the DNA sequence of an organism
  • they can be insertion, deletion, substitution or inversion of base pairs
  • this can be advantageous / disadvantageous / have no effect
  • mutations are caused at random, or by ionising radiation and mutagenic chemicals (carcinogens)

-rapid cell growth of mutated cells can form cancerous tumours
benign tumours grow slowly / are easily removed / do not invade other parts of the body

-malignant tumours grow rapidly / more difficult to remove / do invade other parts of the body