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IGCSE Biology > 17. Inheritance > Flashcards

17. Inheritance Flashcards

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1
Q

What are chromosomes made of?

A

DNA

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2
Q

What does DNA contain?

A

genetic information in the form of genes

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3
Q

What is a gene?

A

a length of DNA that codes for a protein

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4
Q

Where is genetic information in the form of genes contained?

A

DNA

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5
Q

A length of DNA that codes for a protein is…

A

a gene

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6
Q

What is an allele?

A

an alternative form of a gene

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7
Q

A girl would have ____ chromosomes.

A

XX

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8
Q

An alternative form of a gene is…

A

an allele

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9
Q

A boy would have _____ chromosomes.

A

XY

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10
Q

What is a chromosome?

A

thread-like structure of coiled DNA

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11
Q

What is DNA? What does it do?

A
  • a large molecule made from bases
  • carries genetic information in the form of genes
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12
Q

Which gametes are contained in sperm cells?

A

X or Y

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13
Q

Which gametes are contained in egg cells?

A

X

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14
Q

What is the structure of DNA?

A
  • two strands coil together to form double helix
  • each strand contains bases (chemicals)
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15
Q

What is a genetic code?

A

the sequence of bases in a gene

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16
Q

What does the genetic code determine?

A

the sequence of amino acids used to make a specific protein

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17
Q

What determines the sequence of amino acids used to make a specific protein?

A

the sequence of bases in a gene

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18
Q

What does the sequence of bases in a gene determine?

A

the sequence of amino acids used to make a specific protein

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19
Q

What gives different shapes to protein molecules?

A

different sequences of amino acids

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20
Q

Different sequences of amino acids give…

A

different shapes to protein molecules

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21
Q

What is the role of DNA?

A

controlling cell function by controlling the production of proteins

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22
Q

What are some types of protein?

A
  • enzymes
  • membrane carriers
  • antibodies
  • receptors for neurotransmitters
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23
Q

Explain how a protein is made.

A
  1. a DNA molecule in the nucleus unzips, exposing the bases in a gene
  2. mRNA molecule formed using the exposed bases of the DNA strand as a template
  3. bases in mRNA molecule pair with complementary bases in the DNA, so the mRNA molecule now carries a copy of the gene
  4. mRNA molecule moves out of the nucleus into the cytoplasm
  5. ribosome reads the mRNA code
  6. ribosome joins amino acids together to form a protein, following the specific sequence of bases in the mRNA
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24
Q

Why are many genes in a particular cell not expressed?

A

because the cell only makes the specific proteins it needs

25
Q

What do most body cells in an organism contain?

A

the same genes

26
Q

The same genes are contained in…

A

most body cells

27
Q

A cell only makes the specific proteins it needs. Therefore…

A

many genes in a particular cell are not expressed

28
Q

What is a haploid nucleus?

A

a nucleus containing a single set of chromosomes

29
Q

What is a diploid nucleus?

A

a nucleus containing two sets of chromosomes

30
Q

In a diploid cell, there is a pair of each type of ______.

A

chromosome

31
Q

How many chromosomes are in a human diploid cell?

A

23 pairs, 46 chromosomes:
a pair of each type of chromosome

32
Q

Define mitosis.

A

nuclear division giving rise to genetically identical cells

33
Q

What are some roles of mitosis?

A
  • growth
  • repair of damaged tissues
  • replacement of cells
  • asexual reproduction
34
Q

What determines the sequence of amino acids in a protein?

A

the sequence of bases on an mRNA molecule

35
Q

What molecule carries genetic information from the nucleus to the cytoplasm?

A

mRNA

36
Q

What must happen before mitosis takes place?

A

the exact replication of chromosomes
(so that there are two copies of each chromosome when the cell is about to divide)

37
Q

Outline the process of mitosis.

A
  1. two copies of each chromosome are joined together near the middle
  2. nucleus divides into two
  3. one copy of each chromosome goes into each new cell
  4. this keeps the number of chromosomes in the two daughter cells the same as in the original cell
38
Q

What happens during mitosis?

A

the copies of chromosomes separate, maintaining the chromosome number in each daughter cell

39
Q

Define stem cells.

A

unspecialised cells, divide by mitosis to produce daughter cells. these daughter cells can become specialised for specific functions

40
Q

What is the role of meiosis?

A

production of gametes

41
Q

Describe meiosis.

A

reduction division: the chromosome number is halved, resulting in genetically different cells

42
Q

Define inheritance.

A

the transmission of genetic information from generation to generation

43
Q

Define genotype.

A

the genetic make-up of an organism and in terms of the alleles present

44
Q

The genetic make-up of an organism and in terms of the alleles present is…

A

the genotype

45
Q

The transmission of genetic information from generation to generation is…

A

inheritance

46
Q

Define phenotype.

A

the observable features of an organism

47
Q

The observable features of an organism is…

A

phenotype

48
Q

What does the term homozygous mean?

A

having two identical alleles of a particular gene

49
Q

What causes pure breeding?

A

two identical homozygous individuals that breed together

50
Q

What does the term heterozygous mean?

A

having two different alleles of a particular gene

51
Q

Which type of individual will not be pure-breeding?

A

heterozygous

52
Q

Heterozygous individuals will NOT be…

A

pure-breeding

53
Q

What is a dominant allele?

A

an allele that is always expressed if it is present in the genotype

54
Q

What is a recessive allele?

A

an allele that is only expressed when there is no dominant allele present in the genotype

55
Q

What is a test cross?

A

a cross with a homozygous recessive individual

56
Q

What is a test cross used for?

A

to determine the genotype of an individual showing the dominant trait, to find out whether it has DD or Dd

57
Q

What is codominance?

A

a situation in which both alleles in heterozygous organisms contribute to the phenotype

58
Q

What is a sex-linked characteristic?

A
  • feature in which the gene responsible is located on
    a sex chromosome
  • makes the characteristic more common in one sex than in the other
59
Q

What is a an example of sex linkage?

A

red-green colour blindness

IGCSE Biology (28 decks)

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