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Gcse Biology > Genetics ( Test 3) > Flashcards

Genetics ( Test 3) Flashcards

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1
Q

What is sexual reproduction

A

The process involving the fusion of the nuclei of two gametes to form a zygote (fertilised egg cell) and the production of offspring that are genetically different from each other

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2
Q

Names of sex cells in plants and animals

A

Animal- Sperm and Ovum
Plant- Pollen nucleus and Ovum

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3
Q

How many chromosomes does a gamete have and what do we call them

A

23 chromosomes ( haploid)

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4
Q

What is asexual reproduction

A

The process resulting in genetically identical offspring (clones) being produced from one parent

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5
Q

What is binary fission

A

When bacteria produces exact genetic copies of them self by asexual reproduction which creates 2 identical daughter cells.

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6
Q

What type of cell division is needed for asexual reproduction

A

Mitosis

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7
Q

What type of cell division is needed for sexual reproduction

A

Meiosis

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8
Q

What is a genome

A

The entire set of the genetic material of an organism

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9
Q

What is a gene

A

A section of DNA that codes for a particular sequence of amino acids which form proteins

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10
Q

What is DNA

A

The genetic material found in the nucleus of the cell

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11
Q

What is DNA made up of

A

DNA is a polymer made up of two strands coiled around to make a double helix

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12
Q

What is a nucleotide

A

A nucleotide is made of a sugar and a phosphate group, with one of four different bases, A, C, T or G, attached. The nucleotides join together, forming two strands. These form a double helix structure. The double helix is held together by weak hydrogen bonding between complementary base pairs.

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13
Q

Describe the role of nucleotides in the structure of DNA

A

The phosphate and sugar section of the nucleotides form the ‘backbone’ of the DNA strand (like the sides of a ladder) and the base pairs of each strand connect to form the rungs of the ladder

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14
Q

Name the 2 stages that occur in protein synthesis

A

Transcription and translation

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15
Q

What is transcription

A

It takes place in the nucleus and the strand of mRNA that is formed moves out of the nucleus and into the cytoplasm.

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16
Q

What is translation

A

It takes place in the cytoplasm when the mRNA strand attaches to the ribosome

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17
Q

Name the complementary base pairs in mRNA

A

Cytosine and Guanine
Adenine and Thymine

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18
Q

Name the complementary base pairs in tRNA

A

Cytosine and Guanine
Adenine and Uracil

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19
Q

Describe what occurs in translation

A

This stage of protein synthesis occurs in the cytoplasm. The ribsome reads the code on the mRNA in groups of 3, each triplet of bases/ codon codes for an amino acid

20
Q

Why must DNA first be transcribed into mRNA before it can be translated into a protein

A

DNA cannot travel out of the nucleus to the ribosomes (it is far too big to pass through a nuclear pore) so the base code of each gene is transcribed into an RNA molecule called messenger RNA (mRNA).

21
Q

What is an allele

A

A variation of a gene which can be dominant or recessive

22
Q

Homozygous meaning

A

If the two alleles of a gene are the same we describe the individual as homozygous

23
Q

Heterozygous meaning

A

If the two alleles of a gene are different we describe the individual as heterozyous

24
Q

Genotype meaning

A

The combination of alleles that control each characteristic

25
Q

Phenotype meaning

A

The observable characteristics of an organism

26
Q

Dominant allele meaning

A

A dominant allele is always expressed even if only one copy is present

27
Q

What is monohybrid inheritance

A

Inheritance of characteristics controlled by a single gene

28
Q

Is the male or female responsable for determining the sex of the child?

A

Male because female chromosomes are XX whereas male chromosomes are XY

29
Q

What are the four main blood groups?

A

A, AB, B, O

30
Q

Is blood type O the recessive or dominant allele?

A

Recessive

31
Q

Explain what polygenic means and give an example

A

Characteristics that are controlled by more than one gene an example of this is eye colour

32
Q

Define variation

A

Differences between individuals of the same species

33
Q

What is continuous variation?

A

Continuous variation is when there are very many small degrees of difference for a particular characteristic between individuals and they are arranged in order and can usually be measured on a scale. Examples include height, mass, finger length

34
Q

What is continuous variation?

A

Continuous variation is when there are very many small degrees of difference for a particular characteristic between individuals and they are arranged in order and can usually be measured on a scale. Examples include height, mass, finger length

35
Q

What is discontinuous variation

A

Discontinuous variation is when there are distinct differences for a characteristics. For example, people are either blood group A, B, AB or O

36
Q

How is continuous variation found on a graph

A

It has a bell shaped curve

37
Q

Is discontinuous variation usually caused by genetic variation or environmental variation or both?

A

Genetic variation

38
Q

Is continuous variation usually caused by genetic variation or environmental variation or both?

A

Both, genetic and environmental variation

39
Q

Define a zygote

A

Fertilisation is the fusion of the nucleus of a male gamete with the nucleus of a female gamete, producing a new cell called a zygote

40
Q

Define phenotypic variation and what can it be caused by

A

Phenotypic variation is the difference in features between individuals of the same species. It can be caused by genetic and environmental variation.

41
Q

Compare mitosis and meiosis

A

Meiosis produces four genetically different daughter cells while mitosis produces two genetically identical daughter cells. Meiosis produces haploid cells, mitosis produces diploid cells

42
Q

What is found in the nucleus of eukaryotic cells?

A

Chromosomes which are long coiled up molecules of DNA

43
Q

What takes place in sexual reproduction?

A

At fertilisation the male gamete fuses with the female gamete to form a fertilised egg known as a zygote which is diploid. The zygote then undergoes cell division by mitosis and develops into an embryo ( which inherits characteristics from both parents as it has a mixture of chromosomes).

44
Q

Descrbe what happens in meiosis

A

Before the cell divides it duplicates DNA so there is enough for the new cell. In the first division the chromosomes line up in pairs in the centre in a pair there is both a mother and father chromosome. The pairs are pulled apart. In the second division the chromosomes line up at the centre and the chromatids are pulled apart. You get four genetically different haploid daughter cells which are gametes as they have a single set of chromosomes.

45
Q

Define mutations

A

Mutations are rare, random changes that occur in the sequence of DNA bases in a gene or a chromosome

Gcse Biology (4 decks)

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