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IGCSE Biology Part 3 > Reproduction and Inheritance > Flashcards

Reproduction and Inheritance Flashcards

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1
Q

how do alleles create differences in inherited characteristics?

A

alleles can be dominant (represented in genetics by a capital letter) or recessive (represented by a lower case letter) A=dominant a=recessive

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2
Q

what things can mitosis occur during?

A
  1. growth- to create more cells eg. skin cells allowing the body to grow
  2. repair- to replace damaged or dead cells
  3. cloning- to create replicas of a specific cell
  4. asexual reproduction- asexual reproduction means that there is only one parent, so the offspring are identical to that parent
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3
Q

what is the diploid number of chromosomes in human cells?

A

46

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4
Q

what is the haploid number of chromosomes?

A

23

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5
Q

how many chromosomes do gametes have?

A

23- so they can fuse with another 23 during fertilisation and produce a zygote

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6
Q

what environments are asexual and sexual reproduction best suited to?

A 
sexual= changing
asexual= stable
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7
Q

what are the roles of testosterone in the development of secondary sexual characteristics?

A
  • production of sperm
  • growth of sexual organs
  • body hair- pubic, arms, face
  • body mass will increase, including muscle mass
  • voice breaks
  • development of sexual drive
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8
Q

what are the roles of oestrogen in the development of secondary sexual characteristics?

A
  • the beginning of the menstrual cycle
  • body mass increases and redistributed- hips/chest
  • body hair- pubic
  • voice deepens slowly
  • development of sexual organs
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9
Q

what does mitosis do?

A

it produces two new cells that are identical to each other, and to the parent cell

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10
Q

what is found in the nucleus of a cell?

A

the nucleus of a cell contains genetic material, in the form of chromosomes. Chromosomes are long lengths of DNA coiled up.

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11
Q

what is a gene?

A

genes are shorter regions of DNA (a section of a molecule of DNA)

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12
Q

what is the purpose of genes?

A

genes carry the genetic code for a particular characteristic, cell activity or production of a particular protein

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13
Q

what is the meaning of homozygous?

A

individuals who are homozygous for a certain gene carry two copies of the same allele eg. BB or bb

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14
Q

what is the meaning of heterozygous?

A

individuals who are heterozygous for a certain gene carry two different alleles eg. Bb or bB

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15
Q

what is a punnet square?

A

https://qph.fs.quoracdn.net/main-qimg-10a8395561bd7765fda6ca0a5e16c96e-c

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16
Q

what are the differences between sexual and asexual reproduction?

A

in sexual reproduction, two parents create non-identical offspring, inheriting characteristics from both parents. In asexual reproduction a single parent creates genetically identical offspring

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17
Q

how is gender determined?

A

the 23rd chromosome pair is the one that determines whether you are male or female. Every male has ‘XY’ as his 23rd pair and every female has ‘XX’. 50% chance of being male or female

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18
Q

what is the meaning of dominant?

A

a characteristic which will show up in the offspring even if only one of the alleles is inherited

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19
Q

what is the meaning of recessive?

A

a characteristic which only shows up in an offspring when both the alleles are inherited

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20
Q

describe the structure and functions of the male reproductive system

A
  • prostate- add fluid to the sperm; this compound is semen
  • sex glands- add nutrients to the sperm; this is semen
  • sperm duct- sperm travels down this tube to be mixed with nutrients from the glands
  • urethra- allows urine and sperm down to exit the body
  • testis- produce sperm by meiosis and produce testosterone
  • penis- injects sperm into the vagina
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21
Q

how are wind pollinated flowers adapted for pollination?

A
  • small/dull petals as insects don’t need to be attracted
  • no scents or nectaries
  • small, light pollen grains (and lots of them) so they can easily be carried by the wind
  • long filaments that hang the anthers outside the flower so that lots of pollen gets blown away
  • a big feathery stigma to catch pollen carried past by the wind
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22
Q

how is fruit formed?

A
  1. the pollen grain lands on the stigma of another flower of the correct species
  2. pollen tube begins to grow through the style to the ovule
  3. nucleus from male gamete of the pollen passes along the pollen tube, then fuses with the nucleus of the ovule (female)
  4. this fertilises the ovule, forming the seed (zygote)
  5. the ovule wall becomes the seed coat
  6. the ovaries become the fruit
  7. then comes germination, a process controlled by enzymes
23
Q

how are insect pollinated flowers adapted for pollination?

A
  • brightly coloured petals to attract insects
  • scented flowers and nectaries, to attract insects
  • big and sticky pollen grains to easily stick to insects as they fly from plant to plant
  • sticky stigma so any pollen picked up from other plants will stick easily
24
Q

what are the roles of each part of a plant?

A
  • the anther- contains pollen grains (these produce the male gametes)
  • the filament- holds up the anther so they are easily reached by insects brushing against them
  • the stigma- the sticky bit where the pollen grains attach to
  • the style- supports the stigma
  • the ovary- contains the female gametes
25
Q

what is the meaning of codominance?

A

two alleles which are both expressed in the phenotype of an organism

26
Q

what is an allele?

A

an allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome

27
Q

explain the division of a diploid cell by mitosis?

A
  1. cells get the signal to divide; DNA forms X-shaped chromosomes to duplicate itself
  2. chromosomes line up at the centre of the cell; cell fibres pull the chromosomes apart
  3. membranes form around each of the sets of chromosomes, which become the nuclei of the new cells
  4. then, the cytoplasm divides
28
Q

how can plants artificially reproduce?

A

cuttings:

  • a branch is cut off the parent cell
  • the stem is planted in damp compost, with hormones often used (to encourage new roots to develop)
  • the cuttings are covered in a clear plastic bag to keep it warm and moist
  • after a few weeks, new roots develop and then the new plant is produced
29
Q

explain the process of meiosis

A
  1. before division, DNA is duplicated
  2. first division: chromosomes line up in pairs at the centre of the cell
  3. pairs are pulled apart by cell fibres; each new cell has only one copy of each chromosome- some of the mother’s and father’s chromosomes. This mixture of chromosomes gives the offspring variation
  4. second division: chromosomes line up again in the centre of the cell, and the arms of the chromosomes get pulled apart
  5. this results in four haploid gametes, which only have a single set of chromosomes
30
Q

what does the word ‘reproduction’ mean?

A

the ability of living things to produce new living things of the same species

31
Q

describe the structure and functions of the female reproductive system

A
  • oviduct/fallopian tube- egg travels down this tube when matured, where the egg is fertilised
  • vagina- muscular tube between the cervix outside the body, where the penis will enter
  • cervix- muscular ring at the bottom of the uterus that keeps the baby in until it is ready to be born
  • ovary- where the eggs are released from meiosis
  • urethra- tube that carries urine out of the body
  • uterus (womb)- where the foetus grows surrounded by amniotic fluid
32
Q

explain the menstrual cycle

A
  • when a woman is fertile, she produces an egg about every 28 days
  • day 1: woman sheds the lining of the uterus with some blood, called menstruation. This will happen until pregnancy
  • follicle stimulating hormone (FSH) is produced in the pituitary gland, causing ovulation
  • follicle cells produce the hormone oestrogen; level of oestrogen rises in the first 14 days, as new lining is formed and thickens in the uterus
  • oestrogen also stops FSH being produced, so only one egg matures in a cycle
  • Day 14: the hormone luteinizsng hormone causes the follicle cells (in the ovary) to switch from oestrogen to produce progesterone. Maintaining the uterus lining
33
Q

explain fertilisation

A

gametes are sex cells: the male one being sperm; the female one being the egg. When they join together it is known as fertilisation. At this point the fused gametes become a zygote. The zygote then divided repeatedly, at this stage it becomes an embryo after the zygote has undergone cell division

34
Q

how can micropropagation be used to make clones of commercial quantities?

A

any plant can be selected with the most desirable characteristics. After clippings being taken and put into a growth medium, a plant with identical DNA can be produced (a clone). Meaning that every clipping from that desired plant will become a clone with identical characteristics. The more clippings taken, the more clones

35
Q

describe the process of micropropagation

A
  1. a parent plant is chosen with desired characteristics (disease-free)
  2. a small part of the growing tip is removed, because it has actively dividing cells
  3. growing tip is sterilised, to kill any bacteria
  4. growing tip is cut into many pieces, to make many plants
  5. it’s grown in vitro: put into plates of sterile agar jelly (provides an ideal medium for the plant) with lots of nutrients and growth hormones (that stimulate plant cells to rapidly divide)
  6. cells divide and grow into small plants
  7. small plants taken out of the medium, planted into soil and put into glasshouses
36
Q

what is the meaning of genotype?

A

the genetic make up of an organism concerning the alleles of a particular gene eg. TT or Tt or tt

37
Q

what is the meaning of phenotype?

A

the physical characteristics of an organism with respect to one or more particular genes

38
Q

how is a DNA molecule structured?

A

a DNA molecule has 2 strands coiled together, in the shape of a double helix (two spirals). The 2 strands are held together by chemicals called bases:
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
A-T and C-G are complementary base pairings, you find equal amounts of both

39
Q

how can plants naturally asexually reproduce?

A
  1. runners- a second stem extends, and when it reaches the ground, the cell specialises into root cells and the new plant develops eg. strawberries
  2. bulbs- some plants naturally develop food storage organs, which later develop into plants eg. potato tubers, daffodil bulbs
40
Q

what are the roles of oestrogen and progesterone in the menstrual cycle?

A

oestrogen- produced in the ovaries; thickens the womb lining; prompts the release of luteinising hormone
progesterone- produced in the corpus lutiem; maintains the lining of the womb

41
Q

when does mitosis occur?

A
  • when exact copies of already existing cells need to be formed
  • it is also the way certain organisms reproduce through asexual reproduction. Mitosis is a type of cell division
42
Q

what does meiosis produce?

A

four haploid cells, each with half the number of chromosomes, that aren’t identical. Meiosis only happens in reproductive organs to make genetically different haploid gametes

43
Q

why does random fertilisation produce genetic variation of offspring?

A

fertilisation in humans produce huge variations in sex cells, since they’re produced by meiosis; there’s random selection of genetic information from each parent as well. Fertilisation is very random, because there are billions of sperms that could fertilise the ova produced by the female

44
Q

how can variation be genetic?

A

variation in a species can be causes by genetics by the inheritance of genes and alleles from parents:

  • eye colour
  • hair colour
  • blood type
  • inherited disorders
45
Q

how can variation be environmental?

A

variation in a species can be caused by environmental factors, causing organisms to adapt or change:

  • lifestyle
  • climate
  • diet
  • culture
46
Q

how can variation be genetic and environmental?

A

variation can be influenced by both genetic and environmental factors as although genes decide what characteristics we inherit, out surrounding environment will effect how these inherited characteristics develop

eg. plants: plants may have the potential for strong growth, but if they do not receive sufficient mineral resources from the soil, they may hardly grow at all
child: a child might inherit the tendency to be tall, but a poor diet during childhood will cause poor growth

47
Q

what is a mutation?

A

mutations are rare and random changes to the genetic code of a person. It can be inherited. This is done by changing the sequence of the DNA bases, which could stop the production of a specific protein/produce a different kind of protein, leading to new characteristics

48
Q

are mutations harmful?

A

mutations are usually harmful; if it occurs in reproductive cells, offspring may develop abnormally or die. If it occurs in body cells, mutant cell may start multiplying uncontrollably and invade other part of the body (cancer). Some mutations occur in unimportant parts of DNA, making the mutation neutral. Some mutations could be beneficial, such as giving organisms a survival advantage

49
Q

why does resistance to antibiotics increase bacterial populations?

A

bacteria can evolve over time and become anti-biotic resistant

  • bacteria can develop random mutations, which can change their characteristics
  • it’s an advantage for bacteria to resist antibiotics, as it’s able to survive better and live longer, as well as reproduce many more times
  • it leads to the gene of resistance being passes on to offspring (natural selection, meaning that this gene eventually becomes more common in the bacteria population)
50
Q

why does an increase in bacterial populations make infections difficult to control?

A

it is a problem for people infected with these bacteria as they’re hard to get rid of with antibiotics. Sometimes drug companies may come up with a newer more effective antibiotic however ‘superbugs’ that are resistant to most known antibiotics are becoming more common

51
Q

what is evolution?

A
  • evolution is the gradual change in the genetic make up of living things over time
  • one of the mechanism by which living things change is through natural selection
52
Q

what is natural selection?

A

the process whereby organisms better adapted to the environment tend to survive and produce more offspring

53
Q

what are the key points of evolution?

A
  • individuals in a species show a wide range of variation
  • this variation is because of differences in genes
  • individuals with characteristics most suited to the environment are more likely to survive and reproduce
  • the genes that allowed the individual to be successful are passed to the offspring in the next generation

IGCSE Biology Part 3 (1 decks)

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