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Edexcel IGCSE Biology > Inheritance > Flashcards

Inheritance Flashcards

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1
Q

Genome def.

A

The entire genetic material of an organism

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2
Q

What is a Gene

A

A gene is a section of DNA found on a chromosome which codes for a specific protein

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3
Q

Where are chromosomes located

A

In the nucleus of a cell

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4
Q

What do Chromosomes consist of?

A

They consist of genes strung together with associated proteins

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5
Q

What does DNA stand for

A

Deoxyribonucleic acid

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6
Q

How many chromosomes do we have in each cell

A

46 (23 pairs of two identical chromosomes)

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7
Q

How many chromosomes do gametes (sperm and egg cells) have?

A

23 single chromosomes

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8
Q

DNA definition

A

DNA is the molecule that contains the instructions for growth and development of all organisms

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9
Q

What does DNA consist of (structure)

A

It consists of two strands of DNA wound around each other in a double helix

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10
Q

What are the individual units of DNA called

A

nucleotides

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11
Q

What are nucleotides

A

Units of DNA which all contain the same phosphate and deoxyribose sugar, but differ from each other in the base attaches

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12
Q

Four bases

A

Adenine, Thymine, Cytosine, Guanine

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13
Q

Base pairings

A

Adenine-Thymine

Cytosine-Guanine

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14
Q

What does RNA stand for

A

Ribonucleic acid

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15
Q

How is RNA different to DNA

A
  • It contains a single strand of nucleotides
  • Has the base uracil
  • Contains the sugar ribose
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16
Q

What are nucleotides of RNA

A

The nucleotides are similar to those of DNA, consisting of a phosphate, a sugar and a base, however the sugar is ribose rather than the deoxyribose found in DNA (

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17
Q

What are the bases found in RNA

A

Adenine, Uracil, Cytosine, Guanine

18
Q

What is the function of RNA

A

The function of RNA is to transfer the code for proteins found in DNA out of the nucleus and carry it to the ribosomes in the cytoplasm which make the proteins

19
Q

How many types of RNA are involved in the making of proteins

A

Three types

20
Q

What is Transcription

A

TRANSCRIPTION OCCURS IN THE NUCLEUS

Proteins are made by ribosomes with the sequence of amino acids controlled by the sequence of bases contained in DNA
DNA cannot travel out of the nucleus to the ribosomes so the base code is transcribed onto an RNA molecule called messenger RNA (mRNA)

21
Q

What is translation

A

mRNA then moves out of the nucleus and attaches to a ribosome
The ribosome ‘reads’ the code on the mRNA in groups of three (known as a codon)
There is a specific triplet of bases in mRNA known as a ‘start codon’ which indicates to the ribosome that following this, the code for amino acids for this protein will begin
Each codon following the start codon codes for a specific amino acid
In this way the ribosome translates the sequence of bases into a sequence of amino acids that make up a protein
As each codon moves into the ribosome to be translated, a second type of RNA called transfer RNA (tRNA) moves in to match its complementary base pairs to the codon on the mRNA
The site on tRNA that matches to the mRNA codon is known as the anticodon
If the anticodon contains three complementary bases to the codon, the tRNA remains in place and the amino acid attached to it at the other end forms a bond with the next amino acid in line
In this way, the chain of amino acids that make up the protein is formed
As each tRNA molecule releases its amino acid after bonding, it exits the ribosome and moves off to pick up another amino acid
The last codon of the mRNA contains a triplet of bases in a sequence known as a ‘stop codon’
This indicates to the ribosome that the amino acid chain is now complete and can be released to fold and form the final structure of the protein

22
Q

What is an allele

A

Alleles are variations of the same gene

23
Q

What are the two types of alleles

A

Dominant and recessive

24
Q

What is the physical characteristic of an allele called

A

phenotype

25
Q

What is the combination of alleles that control each characteristic called

A

Genotype

26
Q

What are homozygous alleles

A

Two of the same alleles

27
Q

What are heterozygous alleles

A

Two different alleles

28
Q

What is codominance

A

When some genes have alleles that are equally dominant so are both expressed equally in the phenotype

29
Q

What does polygenic mean

A

When characteristics are controlled by more than one gene

30
Q

What kind of phenotypes do polygenic characteristics have

A

Phenotypes which show a wide range of combinations

31
Q

What is an example of polygenic inheritance

A

Eye colour

32
Q

What is monohybrid inheritance

A

The inheritance controlled by a single gene

33
Q

How do we calculate the probability in monohybrid inheritance

A

Using a punnett square (Genetic cross diagram)

34
Q

What are family pedigree diagrams used for

A

Tracing the pattern of inheritance of a specific characteristic (usually a disease) through generations of a family

35
Q

Examples of genetic disorders

A
  • Huntington’s disease
  • Haemophilia
  • Cystic fibrosis
36
Q

How are males and females represented in a family pedigree chart

A

Males are represented with a square and females are represented with circles

37
Q

Female sex chromosomes

A

XX

38
Q

Male sex chromosomes

A

XY

39
Q

When does mitosis occur

A
  • Growth (production of new cells)
  • Repair (to replace dead or damaged cells)
  • Asexual reproduction (mitosis produces genetically identical offspring)
40
Q

What is mitosis

A

Mitosis is cell devision where a diploid cell copies itself and divides into two identical diploid daughter cells

41
Q

Describe the process of Mitosis

A
  • Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x – shaped chromosomes)
  • Chromosomes line up along the centre of the cell where cell fibres pull them apart
  • The cell divides into two; each new cell has a copy of each of the chromosomes

Edexcel IGCSE Biology (1 decks)

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