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Inheritance, Variation and Evolution Flashcards

DNA, protein synthesis, mutations, reproduction, X and Y chromosomes

1
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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2
Q

What does DNA contain?

A

Contains coded information for putting together and operating an organism

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3
Q

Where is DNA located in animal and plant cells?

A

In the nucleus

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4
Q

What are chromosomes?

A

Long structures made of DNA that usually come in pairs

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5
Q

What is the structure of DNA?

A
  • its made up of two strands coiled together in the shape of a double helix
  • its a polymer
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6
Q

What is a gene?

A

A small section of DNA found on a chromosome

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7
Q

What does a gene code for?

A

A particular sequence of amino acids to make a specific protein

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8
Q

How many amino acids are used to make proteins?

A

20 amino acids

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9
Q

What is a genome?

A

The entire set of genetic material in an organism

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10
Q

Why is understanding the human genome important?

A
  • It helps identify genes linked to diseases and knowing which genes are linked to inherited diseases could help us understand them better and develop effective treatments
  • Scientists can trace the migrations of certain populations by looking at the differences in genomes ( as different populations of people migrated away from Africa, they gradually developed small differences in their genomes. By investigating these differences scientists can work out when new populations split off )
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11
Q

What is DNA made up of?

A

lots of repeating units called nucleotides

DNA strands are polymers made up of many repeating units called nucleotides.

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12
Q

What three components make up a nucleotide?

A

Sugar, phosphate group and base

Each nucleotide consists of a sugar, a phosphate group, and one base.

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13
Q

What forms the backbone of DNA strands?

A

Sugar-phosphate groups

The sugar and phosphate groups in the nucleotides form a backbone to the DNA strands.

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14
Q

Which bases pair together in DNA?

A
  • A-T always pair together and C-G always pair, this is called complementary base pairing
  • each base links to a base on the opposite strand

A always pairs up with T, and C always pairs up with G, which is called complementary base pairing.

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15
Q

What determines the order of amino acids in a protein?

A

The order of bases in a gene

The sequence of three bases in a gene codes for each amino acid.

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16
Q

What are non-coding parts of DNA responsible for?

A

Switching genes on and off

Some non-coding parts control whether or not a gene is expressed.

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17
Q

What role does mRNA have?

A

(Carries the code from DNA to ribosomes)
- To make proteins, ribosomes use the code in the DNA.
- DNA is in the nucleus but it cant move out because its too big.
- So the molecule mRNA copies the code from the DNA and carries the code between the DNA and ribosomes.
- The correct amino acids are brought to the ribosomes in the correct order by carrier molecules.

mRNA is made by copying the code from DNA and acts as a messenger.

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18
Q

Where are proteins made in the cell?

A

Ribosomes

Proteins are synthesized in the cell cytoplasm on ribosomes.

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19
Q

What are the functions of different proteins?

A
  • Enzymes act as a biological catalyst to speed up chemical reactions in the body
  • hormones are used to carry messages around the body
  • structural proteins are physically strong

Examples of protein types include enzymes that act as biological catalysts, hormones that carry messages, and structural proteins like collagen.

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20
Q

What is a mutation?

A

A random change in an organism’s DNA.

Mutations can sometimes be inherited.

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21
Q

What is a genetic variant?

A

A different form of a gene produced by mutations

Mutations change the sequence of DNA bases in a gene.

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22
Q

What happens if the shape of an enzyme’s active site is changed?

A

Its substrate may no longer be able to bind to it.

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23
Q

What effect can mutations in non-coding DNA have?

A

They can alter how genes are expressed.

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24
Q

What is an insertion mutation?

A

Where a new base is inserted into the DNA base sequence where it shouldn’t be. This changes the way the three bases are read which can change the amino acids they code for. They change more than one amino acid as they have a knock on effect.

25
What is a deletion mutation?
When a random base is deleted from the DNA base sequence. They change the way the base sequence is read and have knock on effects.
26
What is a substitution mutation?
When a random base in the DNA base sequence is changed to a different base.
27
Fill in the blank: Changes in bases can affect the _______ sequence, and therefore the protein coded for.
amino acid
28
What is sexual reproduction?
The fusion of male and female gametes during fertilisation. Because there are two parents the offspring contain a mixture of their parents genes. ## Footnote Sexual reproduction involves the fusion of male and female gametes.
29
What are gametes in sexual reproduction?
Cells produced by the mother and father through meiosis, such as egg and sperm cells in animals. ## Footnote Gametes are necessary for fertilization.
30
How does variation occur in offspring?
- In humans each gamete contains 23 chromosomes - the egg and sperm cell then fuse together to form a cell with the full number of chromosomes - this is why offspring inherit features from both parents because its received a mixture of chromosomes - the mixture of genetic information created variation ## Footnote This results in half of the chromosomes from each parent.
31
What is asexual reproduction?
A single parent organism produces genetically identical offspring without fusing gametes or mixing chromosomes and there is no genetic variation ## Footnote Asexual reproduction does not involve the fusion of gametes.
32
How do organisms reproduce asexually?
Asexual reproduction occurs by mitosis, where an ordinary cell divides to create a new cell with the same genetic information as the parent. (called a clone) ## Footnote This results in clones of the parent cell.
33
List examples of organisms that reproduce asexually.
- Bacteria - Some plants - Some animals ## Footnote Asexual reproduction is common in simpler life forms.
34
How many pairs of chromosomes are there in every human body cell?
23 pairs ## Footnote 22 pairs are matched chromosomes controlling characteristics, and the 23rd pair determines sex.
35
What are the two types of sex chromosomes?
XY for males and XX for females ## Footnote XY indicates male, and XX indicates female.
36
What does the Y chromosome cause?
Male characteristics ## Footnote The presence of the Y chromosome is responsible for developing male traits.
37
What does the XX chromosome combination allow?
Female characteristics to develop ## Footnote The two X chromosomes lead to the development of female traits.
38
What happens to the X and Y chromosomes during sperm formation?
They are drawn apart in the first division in meiosis. There's a 50/50 chance the sperm cell will receive a X and Y chromosome ## Footnote This occurs during the first division in meiosis.
39
How many X chromosomes does the original cell have when making eggs?
Two X chromosomes. So all the eggs have one X chromosome ## Footnote All egg cells will receive one X chromosome from this original cell.
40
What do genetic diagrams show?
Possible gamete combinations ## Footnote These diagrams illustrate the potential outcomes of gamete formation.
41
what do genes control?
the characteristics you develop
42
what are alleles?
- different versions of the same gene - you have versions (alleles) of every gene in your body
43
What is heterozygous?
alleles are both different for a particular gene
44
What is homozygous?
alleles are identical for a particular gene
45
What allele overrules if it is present?
the dominant allele overrules the recessive allele if it is present and will show dominant characteristics
46
What is a genotype?
the combination of alleles an organism has for a particular characteristic, this can be expressed by your phenotype
47
What is a phenotype?
the physical characteristics of an organism
48
How are gametes produced?
meiosis
49
What are the steps of meiosis?
- The cell duplicates its genetic information forming two armed chromosomes - one is an exact copy of the other arm - The chromosomes arrange themselves into pairs - In the first division the pairs line up in the centre of the cell - The pairs are pulled apart and the cell splits into two new cells, so each new cell only has one copy of each chromosome - Some of the mothers and fathers chromosomes randomly go into each new cell - In the second division the chromosomes line up again in the centre - the arms of the chromosomes are pulled apart dividing the cells into four gametes each with only a single set of chromosomes in it - Each gamete is genetically different because the chromosomes all get shuffled up during meiosis and each gamete only gets half at random (23 chromosomes)
50
What happens after gametes fuse together?
- After two gametes fuse during fertilisation, the new cell divides by mitosis to make a copy of itself - Mitosis repeats many times to produce lots of new cells in an embryo - These cells start to differentiate into the different types of specialised cells that make up a whole organism
51
What are the advantages of sexual reproduction
- Offspring have a mixture of chromosomes which produces variation, increasing the chance of a species surviving a change in the environment. Because individuals with characteristics that make them better adapted to the environment have a better chance of surviving, they are more likely to breed successfully and pass the genes for the characteristic on. ( natural selection) - We can use selective breeding allowing us to produce animals with desirable characteristics. This means we can increase food production e.g. by producing animals that have a lot of meat
52
What are the advantages of asexual reproduction?
- Only one parent meaning it uses less energy because organisms don't have to find a mate - Faster - Many identical offspring can be produced in favourable conditions
53
What organisms can reproduce sexually and asexually?
- Malaria, the parasite reproduces sexually in the mosquito and asexually when its in the human host - Lots of species of plant produces seeds sexually but also asexually for example plants that grow from bulbs e.g. daffodils. new bulbs can form from the main bulb and divide off. Each new bulb can grow into a new identical plant - Many species of fungus. Spores which reproduce new fungi can be produced sexually and asexually. Asexually produced spores form fungi that are genetically identical to parent. Sexually produced spores introduce variation and are often produced in response to an unfavourable change in the environment, increasing the chance the population will survive the change.
54
What is Cystic Fibrosis?
A genetic disorder of the cell membranes. It results in the body producing mucus in the air passages and in the pancreas.
55
How is cystic fibrosis caused?
- Its cause by a recessive allele (f) so people with only one copy of the allele wont have the disorder instead they're carriers - For a child to have it both parents must be carriers or have the disorder - There's a 1 in 4 chance of that the child having the disorder if both parents are carriers
56
What is Polydactyly?
A genetic disorder where a baby's born with extra fingers or toes
57
How is Polydactyly caused?
- caused by a dominant allele (D) and can be inherited if just one parent carries the allele - the parent will have the disorder too because the allele is dominant - there's a 50% chance of a child having the disorder if one parent has one D allele
58
What is IVF?
- embryos are fertilised in a laboratory and then implanted into the mothers womb - before being implanted its possible to remove a cell from each embryo and analyse its genes, many genetic disorders can be detected this way

Biology (10 decks)

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