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OCR GATEWAY GCSE BIOLOGY > B5 Genes, inheritance + selection > Flashcards

B5 Genes, inheritance + selection Flashcards

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1
Q

What is the genome?

A

-The entire genetic material of an organism.
-May influence the phenotype when interacting with its environment.
-Arranged as chromosomes and stored in the nucleus.

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2
Q

What is the phenotype?

A

The visual characteristics of an individual.

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3
Q

What is a chromosome?

A

Long, coiled up strand of DNA.

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4
Q

What is a gene?

A

A short section of DNA that codes for a protein and therefore controls / helps other genes control a characteristic.

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5
Q

What is variation?

A

The differences between individuals of the same species caused by genetic and environmental factors.

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6
Q

What are the 2 causes of variation?

A

-Inherited / genetic: offspring inherit characteristics from their parents.
-Environmental: characteristics are impacted by the individual’s surroundings.

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7
Q

Why don’t most mutations influence the phenotype?

A

Most DNA is non coding therefore mutations rarely cause a change in proteins.

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8
Q

What is a mutation?

A

-A random / spontaneous change in the base sequence / quantity of DNA which causes the alleles to change and therefore produces genetic variants.
-Can be harmful / neutral / beneficial.

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9
Q

What causes mutations?

A

Mutagens.

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10
Q

What are coding genes?

A

Genes in the coding region of DNA.

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11
Q

What is regulatory DNA?

A

Genes in the non-coding region of DNA.

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12
Q

How can mutations in coding regions of DNA alter the activity of the protein that the altered DNA is meant to code for?

A

Change the shape of the protein made and make the protein non-functional.

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13
Q

How can mutations in non coding regions of DNA still affect how genes are expressed?

A

By stopping the transcription of mRNA during protein synthesis and therefore stopping the production of the protein altogether.

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14
Q

What is a promoter?

A

An example of regulatory DNA which determines which gene will be expressed.

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15
Q

What are the 3 types of mutation?

A

-Insertion: When a nucleotide is added to the DNA sequence.
-Deletion: When a nucleotide is removed from the DNA sequence.
-Change: When the order of nucleotides is changed.

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16
Q

What is sexual reproduction?

A

A source of variation due to the offspring acquiring half of their genes from each parent.

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17
Q

What is asexual reproduction?

A

A form of reproduction that only requires a single parent and produces genetically identical offspring.

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18
Q

What are the advantages of sexual reproduction?

A

-Variation in offspring leads to adaptations in a species.
-Only some organisms in a population will contain the adaptations required to cope with an environmental pressure and these organisms can reproduce, allowing the population to continue.

19
Q

What are the disadvantages of sexual reproduction?

A

-Requires 2 parents.
-Slower reproduction.
-Requires energy so not energy efficient.

20
Q

What are the advantages of asexual reproduction?

A

-If the parent is well adapted to the area, the offspring will share an identical set of characteristics.
-Only one parent needed so don’t require partner / pollination.
-Faster reproduction so large numbers of offspring produced quickly.

21
Q

What are the disadvantages of asexual reproduction?

A

Adverse changes to the environment may destroy the species as all the organisms are identical and therefore all will be affected.

22
Q

What is meiosis?

A

A form of cell division that produces 4 haploid gametes that are genetically different, ensuring variation in a species.

23
Q

How do cells in the reproductive organs form gametes?

A

They divide by meiosis.

24
Q

What are gametes?

A

Sex cells which have half the number of chromosomes as they only have one copy of each chromosome.

25
Q

What is a haploid cell?

A

Has 1 set of 23 chromosomes.

26
Q

What is a diploid cell?

A

Has 2 sets of 23 chromosomes.

27
Q

What is the process of meiosis?

A
  1. The cell makes copies of its chromosomes so it has double the amount of genetic information.
  2. The cell divides into 2 diploid cells, each with half the amount of chromosomes.
  3. Each cell divides into 2 again to produce 4 haploid cells altogether.
  4. These haploid cells are called gametes and are all genetically different from each other.
28
Q

Why does meiosis result in 4 genetically different haploid cells?

A

The chromosomes are shuffled during the process, resulting in random chromosomes ending up in each of the 4 cells.

29
Q

What are alleles?

A

Different forms of the same gene.

30
Q

Why do humans have 2 alleles for each gene?

A

They inherit one allele from each parent.

31
Q

What is the difference between a dominant allele and a recessive allele?

A

-Only 1 out of 2 alleles needs to be dominant for the dominant allele to be expressed and present in the phenotype.
-Both alleles need to be recessive for the recessive allele to be expressed and present in the phenotype.

32
Q

What is homozygous?

A

When both inherited alleles are the exact same.

33
Q

What is heterozygous?

A

When both inherited alleles are different.

34
Q

What is the genotype?

A

The combination of alleles an individual has.

35
Q

Why do alleles exist in pairs?

A

At the time of fertilisation, one is inherited from the sperm and one from the egg.

36
Q

What are punnet squares?

A

Used to work out the chances of a trait being passed on.

37
Q

How do chromosomes work?

A

-22 pairs of chromosomes control the characteristics and each of these pairs looks very similar.
-23rd pair carries sex determining genes and the 2 chromosomes can look different.
-1 sex chromosome goes into each gamete when cells undergo meiosis.

38
Q

What are the sex chromosomes for a female?

A

XX

39
Q

What are the sex chromosomes for a male?

A

XY

40
Q

What was the work of Gregor Mendel?

A

-He worked in the monastery gardens and observed the characteristics passed on to the next generations in plants.
-He carried out breeding experiments on pea plants using different species and observed the offspring to see which characteristics they inherited.

41
Q

What were Gregor Mendel’s conclusions?

A

-Offspring have some characteristics their parents have because they inherit hereditary units from each.
-One unit is received from each parent.
-Units can be dominant / recessive and can’t be mixed together.

42
Q

When were chromosomes observed as part of cell division?

A

In the late 19th century.

43
Q

When was it discovered that chromosomes and units have similar behaviours and why?

A

In the 20th century and due to units being the genes on the chromosomes.

44
Q

When was the structure of DNA determined so that we could understand how genes worked?

A

1953

OCR GATEWAY GCSE BIOLOGY (6 decks)

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