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Edexcel IGCSE Biology > Inheritance > Flashcards

Inheritance Flashcards

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1
Q

What is the genome?

A

All of the genes present in an organism

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2
Q

What is a gamete?

A

Gametes are sex cells (sperm or eggs)

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3
Q

What is a chromosome?

A

Tightly packaged DNA around histone proteins

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4
Q

How many chromosomes do human body cells have?

A

46 (23 pairs)

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5
Q

How many chromosomes do human gametes have?

A

23 chromosomes

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6
Q

Where are chromosomes located?

A

In the nucleus of the cell

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7
Q

What is a gene?

A

A section of DNA that codes for a protein

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8
Q

Describe the structure of DNA

A
  • It is a polymer made of many nucleotide monomers
  • It is made of 2 strands in the shape of a double helix
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9
Q

Name the 4 bases in DNA

A

Adenine (A), Thymine (T), Cytosine (C) and Guanine (G)

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10
Q

State 2 differences between DNA and RNA

A
  • DNA is double stranded whereas RNA is single stranded
  • RNA contains Uracil (U) whereas DNA contains Thymine (T)
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11
Q

How do the bases in DNA pair up?

A

Adenine pairs with Thymine (A with T)
Cytosine pairs with Guanine (C with G)

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12
Q

Describe transcription

A
  • DNA unzips
  • mRNA nucleotides bind to complementary base pairs of the DNA and are joined together
  • mRNA detaches and leaves the nucleus
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13
Q

What is a codon?

A

A group of 3 bases on the mRNA molecule that code for a single amino acid

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14
Q

What is an anticodon?

A

3 bases on the tRNA molecule that match the codon on the mRNA molecule

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15
Q

Describe translation

A
  • mRNA travles to a ribosome
  • tRNA molecules with an anticodon that matches the codon on the mRNA molecule carry amino acids to the ribosome
  • The amino acids are joined with peptide bonds, forming a peptide chain
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16
Q

How does the sequence of bases affect the protein made in protein synthesis?

A

DNA is a triplet code where 3 bases code for one amino acid and the order of amino acids determine the protein produced

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17
Q

What is an allele?

A

Different versions of the same gene

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18
Q

What is a dominant allele?

A

A version of a gene where only one copy is needed for it to be expressed

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19
Q

What is a recessive allele?

A

A version of a gene where two copies are needed for it to be expressed

20
Q

What is meant when an organism is homozygous?

A

When an organism has two copies of the same allele (two recessive or two dominant)

21
Q

What is meant when an organism is heterozygous?

A

When an organism has two different versions of the same gene (one dominant and one recessive)

22
Q

What is the genotype?

A

The gene present for a trait

23
Q

What is the phenotype?

A

The visible characteristic

24
Q

What is codominance?

A

When two alleles affect the phenotype

25
Q

What is monohybrid inheritance?

A

The inheritance of one allele

26
Q

Draw a Punnett square for a cross between a homozygous recessive blue eyed female (bb) with a heterozygous brown eyed male (Bb)

A
27
Q

Draw a Punnett square for a cross between a homozygous dominant red flower (RR) with a homozygous recessive white flower (rr)

A
28
Q

Draw a Punnett square for a cross between two heterozygous cystic fibrosis carriers (Ff)

A
29
Q

Draw a Punnett square to show how sex is determined

A
30
Q

What do family pedigrees show?

A

The inheritance of an allele over generations

31
Q

Give 3 processes that require mitosis

A
  • Growth
  • Repair
  • Asexual reproduction
32
Q

How many cells does mitosis produce?

A

One parent cell produces 2 daughter cells

33
Q

How many cells does meiosis produce?

A

One parent cell produces 4 daughter cells

34
Q

Give 2 differences between mitosis and meiosis

A
  • Mitosis produces 2 genetically identical cells whereas meiosis produces 4 genetically different cells
  • Mitosis produces diploid cells where as meiosis produces haploid cells
35
Q

What is random fertilisation?

A
  • The random chance of a specific sperm combining with a specific egg
  • This increases variation as any female can mate with any male and any one of the millions of sperm could fertilise the egg
36
Q

What are the two types of variation?

A

Genetic variation and environmental variation

37
Q

State 2 traits in humans caused only by genetic variation

A
  • Eye colour
  • Blood type
38
Q

State 2 traits in humans caused by a mix of environmental and genetic variation

A
  • Height
  • Weight
39
Q

What is a mutation?

A

A random change in the genetic material of an organism

40
Q

How do mutations alter the phenotype?

A
  • Mutations alter the genetic material (DNA)
  • This can cause it to code for a different sequence of amino acids
  • A different sequence of animo acids means that the protein will be different
41
Q

Give 3 environmental factors that can increase the chance of mutations

A
  • Exposure to UV radiation
  • Exposure to X-rays
  • Certain chemicals, particularly those found in cigarette smoke
42
Q

Describe the process of natural selection

A
  • Populations are naturally varied due to random genetic mutations
  • Some of these mutations provide a selective advantage
  • These organisms survive and reproduce, passing on the successful genes
43
Q

Define evolution

A

Evolution is a change in the genetic makeup of a population over time due to natural selection

44
Q

Describe how antibiotic resistance arises

A
  • A random genetic mutation causes a bacterium to become resistant to the antibiotic
  • When the antibiotic is used, all the bacteria that do not have the mutation are killed
  • The population containing just the resistant bacteria then begins to grow
45
Q

What are the risks of antibiotic resistance?

A

Bacteria that causes infections that are resistant to antibiotics are hard to treat and can pose a serious threat to our health

Edexcel IGCSE Biology (31 decks)

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