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AQA Biology Triple Science - All Topics 🧫🔬🧬 > Topic 13 - Reproduction > Flashcards

Topic 13 - Reproduction Flashcards

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1
Q

What are the two types of reproduction?

A

Sexual and asexual reproduction.

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2
Q

What is the main difference between sexual and asexual reproduction?

A

Sexual reproduction requires two organisms to occur, whereas asexual requires only one organism.

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3
Q

What are the important facts about asexual reproduction?

A

-Cells divide by mitosis.
-There is no fusion of gametes.
-Therefore there is no mixing of genetic material.
-It gives rise to genetically identical offspring known as clones.

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4
Q

Where is asexual reproduction common?

A

-Small animals and plants.
-Fungi and bacteria.
-Larger plants.
-Body cells (for growth and repair).

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5
Q

What are the main facts about sexual reproduction?

A

-It involves a male and female gamete.
-There is fusion of gametes.
-This leads to mixing of genes.
-This leads to variation.
-Variation can lead to evolution.
-Cells made from sexual reproduction inherit genetic informatiom from both parents

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6
Q

What is meiosis?

A

Gametes are made by this process. The number of chromosomes also halves.

Genetic information is copied so there are four sets of each chromosome instead of two sets.

The cell then divides twice rapidly to form four gametes with a single set of chromosomes.

Each gamete produced is genetically different from others. Gametes contain random mixtures of original chromosomes introducing variation.

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7
Q

Explain what happens to variation during fertilisation.

A

More variation is added. Each sex cell has a single set of chromosomes. When two gametes join during fertilisation, the single cell has a full set of chromosomes. In humans, the egg and sperm both have 23 chromosomes. This becomes 46 after fertilisation.

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8
Q

What happens to variation in sexual reproduction?

A

Gametes are produced by meiosis in the parents. This introduces variation as each gamete is different. When the gametes fuse, new combinations of genes arise, creating variation.

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9
Q

What are the advantages of asexual reproduction?

A

-Only one parent is needed
-It is time and energy efficient as there is no need to find a mate.
-It is faster than asexual reproduction.

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10
Q

What are the disadvantages of asexual reproduction?

A

-In the event of an environmental change, no offspring survive due to a lack of variation.
-A lack of variation also means that a species cannot evolve.

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11
Q

What are the disadvantages of sexual reproduction?

A

-Two parents are needed
-It takes more time and energy

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12
Q

What are the advantages of sexual reproduction?

A

-It produces variation in offspring due to the fusion of gametes
-It can lead to evolution by natural selection
-In the event of a pathogen spreading, due to variation, some members may have resistance and pass on their advantageous genes.

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13
Q

What is the most common form of reproduction in fungi?

A

Asexual.

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14
Q

How does asexual reproduction work in fungi?

A

Fungal spores are produced by mitosis that are genetically identical to the parent.

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15
Q

When do fungi reproduce sexually?

A

When conditions are not optimal, for example in dry conditions.

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16
Q

What happens when fungi reproduce sexually?

A

Two hyphae from different fungi join and the nuclei fuse. It undergoes meiosis to make haploid spores, each with different sets of chromosomes.

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17
Q

What does it mean if cells are haploid?

A

They only have one set of chromosomes. In humans this is found in gametes where they have 23 each.

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18
Q

What does it mean if cells are diploid?

A

They have two sets of chromosomes. In humans this is found around the body where there are 23 x 2 chromosomes (46) in each cell made by mitosis.

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19
Q

What happens when flowers go through sexual reproduction?

A

Pollen from one flower must pollenate female parts of another flower. Once pollen fuses with the egg, seeds are formed.

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20
Q

How do plants grow?

A

Directed mitosis.

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21
Q

How do malarial parasites reproduce?

A

They reproduce asexually in human liver and blood cells. When the mosquito takes a blood meal, the drop in temperaturr between the human body and the mosquito triggers sexual reproduction in some parasites. There is a 20 minute window when sexual forms develop, burst out of the blood cells and meet to form diploid zygotes. They undergo meiois to produce nee asexual parasites.

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22
Q

What is DNA?

A

A polymer containing genetic code found in nuclei making up chromosomes.

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23
Q

What are genes?

A

Small sections of DNA

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24
Q

How are specific proteins made?

A

Each gene codes for a particular set of amino acids to make a protein.

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25
Q

What is the Human Genome Project?

A

A project dedicated to sequencint the human genome by reading all DNA bases.

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26
Q

What is the genome?

A

The entire generic material of an organism.

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27
Q

How much DNA is a genome?

A

3 billion bases and 21000 genes that code for proteins.

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28
Q

How many genomes are the Human Genome Project aiming to sequence next?

A

100,000.

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29
Q

Why does the genome matter?

A

-It helps us understand inherited disorders
-It helps us understand which genes are linked to an increased risk of developing diseases.
-It helps us understand human history and migration patterns by seeing genome similarity between groups.

30
Q

What makes up a DNA molecule?

A

Alternating sugar and phosphate sections and one of four DNA bases (ACGT)

31
Q

What is the combination of a sugar, phosphate and DNA base called?

A

Nucleotide

32
Q

What is the DNA polymer made up of?

A

Repeating nucleotides

33
Q

How many bases code for an amino acid?

A

3

34
Q

Describe the process of protein synthesis.

A

-Genes produce a template for the protein reflecting the sequences of bases, but is small enough to leave the nucleus through pores in the membrane.
-The template leaves the nucleus and binds to the surface of a ribosome.
-The cytoplasm contains carrier molecules that attach themselves to the template
-Amino acids are attached to form a protein.
-Carrier molecules add amino acids to the protein chain until the template is complete.
-The protein detaches from the carrier molecules and they detach from the template.
-Once the chain is complete it folds up to form a unique shape enabling it to carry out a certain function.

35
Q

What happens if there is a change in the order of DNA bases?

A

The DNA structure may alter resulting in a different protein being made.

36
Q

What are mutations?

A

Changes in existing genes to alter the order base orders. It normally does not change the protein form.

37
Q

What can happen with mutation in rare cases?

A

There is a change in the amino acids resulting in an altered protein that folds into a different shape. As a result, the active site may no longer fit the substrate.

38
Q

What is genotype?

A

The genetic characteristics of an organism.

39
Q

What is phenotype?

A

The physical characteristics expressed by an organism.

40
Q

What is a homozygote?

A

An individual with two identical alleles - bb or BB.

41
Q

What is a heterozygote?

A

An individual with two different alleles - Bb

42
Q

What is a recessive gene?

A

A gene that is not expressed if the organism is heterozygous and is only expressed if homozygous with that gene - bb

43
Q

What is a dominant gene?

A

A gene expressed when heterozygous with another - Bb - B is dominant.

44
Q

What can we use a Punnett square to do?

A

Predict the outcome of different genetic crosses.

45
Q

What are the sex chromosomes in human females?

A

XX

46
Q

What is the sex chromosome in human males?

A

XY

47
Q

What is polydactyly?

A

A dominant gene where a person is born with an extra finger or toe. It is a dominant gene.

48
Q

What is cystic fibrosis?

A

A genetic disorder affecting many organs. It is a disorder of cell membranes preventing movement of certain substances. Organs like the lungs can be clogged up as a result. The reproductive system is also affected so many are infertile.

49
Q

What is cystic fibrosis caused by?

A

A recessive allele received from both parents who don’t express it but still have the allele?

50
Q

What is an allele ‘carrier’?

A

A parent who carries an allele to their offspring without expressing the gene.

51
Q

How do scientists wish to treat genetic disorders?

A

By using genetic engineering.

52
Q

How does screening embryos work?

A

Cells have to be harvested from one of two sources- amniocentesis and chorionic villus sampling.

53
Q

What is amniocentesis?

A

A process carried out at around 15/16 weeks of pregnancy involving taking fluid from around the developing fetus which contains fetal cells.

54
Q

What is chorionic villus sampling of embryonic cells?

A

A process done at 10-12 weeks of pregnancy by taking a smaller sample of tissue from the developing placenta providing cells.

55
Q

What is the main risk of amniocentesis and chorionic villus sampling?

A

Both have an associated risk of miscarriage.

56
Q

What is an alternative to the other two methods of screening?

A

Embryos produced by IVF are tested before they are implanted into the mother so only babies without the disorder are born.

57
Q

How is screening of cells carried out?

A

DNA from the sample cells is isolated from the embryo and tested for specific disorders.

58
Q

What is a problem with the screening methods?

A

They may give a false positive or negative result resulting in the termination of a healthy pregnancy or an unexpected birth of a child with a genetic abnormality.

People also have to make a decision on terminating a fetus, which could conflict with moral values.

59
Q

What is the financial impact of embryo screening?

A

The processes are very expensive but the cost of caring for a child with a genetic disorder may be more expensive in the future.

60
Q

What are people concerned about happening if we continue to choose characteristics of babies?

A

That designer babies may become a thing and respecting others’ traits may become lost.

61
Q

What bases are there for DNA?

A

CGAT

62
Q

What is the order of events in protein synthesis?

A

The template leaves the nucleus and binds to the surface of a ribosome.

The cytoplasm contains carrier molecules, attached to a specific amino acid. The carrier molecules attach themselves to the template in order.

Amino acids join together to form a protein.

Carrier molecules keep bringing specific amino acids to add to the chain.

The protein detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm to pick up more amino acids.

63
Q

What are the proportions for different genotypes?

A

25% for homozygous dominant (BB)
50% for heterozygous (Bb)
25% for homozygous recessive (bb)

64
Q

What kind of gene is polydactyly?

A

Dominant

65
Q

What type of gene is cystic fibrosis?

A

recessive

66
Q

What is the name for people who have a recessive gene that doesn’t show?

A

carriers

67
Q

What is the proposes solution to genetic disorders?

A

Genetic engineering - replacing faulty genes with healthy ones.

68
Q

What steps can be taken to screen embryos?

A

Amniocentesis at 15-16 weeks into a pregnancy

Chorionic villus sampling of embryonic cells at 10-12 weeks

Producing embryos through IVF to be tested

69
Q

What considerations are there with embryo screening?

A

Reliability of positive and negative results

Ethical decisions

Economic problems

Ethical considerations around ‘designer babies’

70
Q
A

AQA Biology Triple Science - All Topics 🧫🔬🧬 (32 decks)

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