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Biology - IGCSE > Ch 17 - (Inheritance) > Flashcards

Ch 17 - (Inheritance) Flashcards

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1
Q

What is inheritance?

A

Transmission of genetic information from generation to generation.

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2
Q

Where are chromosomes located?

A

Nucleus of the cell

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3
Q

What is a gene?

A

A short length of DNA found on a chromosome that codes for a specific protein

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4
Q

What do genes do?

A
  • Control our characteristics
  • code for proteins
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5
Q

what are alleles?

A

Different versions of a particular gene

  • gives characteristics
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6
Q

what is sex determined by?

A

Entire chromosome pair

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7
Q

What is the female sex chromosome?

A

XX

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8
Q

What is the male sex chromosome?

A

XY

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9
Q

who is responsible for gender of child?

A
  • only father passes Y chromosome
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10
Q

Why is father responsible for determining the gender?

A
  • he ejaculates 250 million sperms during sexual intercourse
  • only 125 million sperms carry X chromosome
  • if one of these sperms fertilize egg, fetus will be female
  • 125 million sperms carry Y chromosome which will result in a boy
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11
Q

How can the inheritance of gender be shown?

A
  • Genetic diagram
  • Punnett Square
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12
Q

what does the DNA base sequence determine?

A
  • Amino acid sequence in protein
  • DNA (a series of bases) is converted into proteins (amino acids )
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13
Q

What are the 2 stages of protein synthesis?

A
  1. Transcription: Rewriting the base code of DNA into bases of RNA
  2. Translation: Using RNA base sequence to build amino acids into sequence in a protein
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14
Q

What are proteins made by?

A
  • Ribosomes with the sequence of amino acids controlled by the sequence of bases contained within DNA
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15
Q

Explain the process of protein synthesis.

A
  • DNA cannot travel out of the nucleus to the ribosomes (too big to pass through a nuclear pore) so base code of each gene is transcribed into RNA molecule called messenger RNA (mRNA)
  • mRNA mass then moves out of the nucleus and attaches to ribosome
  • ribosome ‘reads’ the code on the mRNA groups of three
  • each triplet of bases codes for a specific amino acid
  • ribosomes translate the sequence of bases into sequence of amino acids that make up a protein
  • Once ands, it releases from ribosome so it can fold and form the final structure
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16
Q

What does expression of a gene mean?

A

Whether that gene is transcribed and translated in a particular cell or not

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17
Q

How and why are most genes not expressed in a particular cell?

A
  • they are switched off
  • cuz it’s waste of energy and other resources in the cell
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18
Q

Which proteins are used for protein synthesis?

A
  • only gene whose protein are vital to the cell’s functions are expressed (switched on)
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19
Q

What does DNA do in protein synthesis?

A
  • controls cell function
  • controlling production of proteins
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20
Q

What’s re the diff types of proteins that can be synthesized?

A

Enzymes, antibodies, receptors, neurotransmitter

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21
Q

Why are many genes in a particular cell not expressed?

A

The cell only make specific proteins it needs

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22
Q

How many chromosomes are there in each cell

A

23 diff chromosomes pair

46 in total chromosomes

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23
Q

What is a diploid and haploid cell?

A

Diploid nuclei: Nuclei with 2 sets of chromosomes

Haploid nuclei: One set of unpaired chromosomes

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24
Q

How many chromosomes does each chromosome consist of?

A

23 chromosomes

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25
Q

What is mitosis?

A

The type of cell division is used for growth, repair of damaged tissues, replacement of cells and asexual reproduction.

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26
Q

Define mitosis.

A

Nuclear division giving rise to genetically identical cells

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27
Q

What is the process before mitosis happens?

A
  • each chromosome in the nucleus copies itself (forms X shaped chromosome)
  • chromosomes line up along the center of the cell where cell fibers pull them apart.
  • cell divides into 2, each new cell has a copy of each chromosome
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28
Q

What is the importance of mitosis?

A
  • all cells in the body (excluding gametes) are produced by mitosis of the zygote
  • important for replacing cells and for growth
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29
Q

What does mitosis occur in?

A
  1. Growth: Mitosis produce new cells
  2. Repair: To replace damaged or dead cells
  3. Asexual reproduction: Mitosis produces offspring that’s re genetically identical to parent
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30
Q

What do many tissues in the body contain?

A

Unspecialized cells (stem cells)

31
Q

What is the function of stem cells?

A

Produce new daughter cells that can become specialized within tissue

32
Q

What is the ultimate stem cell?

A

Zygote (Embryonic stem cells) - becomes a ball of unsoecialised cells

33
Q

Define meiosis

A

Nuclear division that gives rise to cells that are genetically different

34
Q

What is meiosis used for?

A

To produce gametes (sex cells)

35
Q

What needs to happen when gametes (sex cells) are formed?

A

Chromosome must be halved

36
Q

When does halving of chromosomes happen?

A
  • Meiosis
  • reduction division
  • chromosome number is halved from diploid to haploid
  • results in genetically different cells
37
Q

What happens in meiosis?

A
  • chromosomes double in mitosis and line up in center of cell
  • cells divide twice so that only one copy of chromosomes is passed onto each gamete
38
Q

What happens in double division?

A
  • Gametes are haploid
  • thsi double division, meiosis produces 4 haploid cells
39
Q

Explain the proper process of meiosis.

A
  • each chromosome makes a copy of itself (X - chromosome)
  • First division: Chromosome pair up along the cell, recombination occurs, cell fibers pull each pair apart, each new cell has one recombinant chromosome pair
  • Second division: Chromosome will line up along the centre of the cell, cell fibres will pull them apart (mitosis)
  • 4 haploid daughter cells
40
Q

What is the importance of meiosis?

A
  • Production of gametes
  • increases genetic variation
  • has variation and has new combinations of maternal and paternal chromosomes
41
Q

What is the difference in the cells produced in mitosis and meiosis?

A

Mitosis: 2 cells produced (daughter cells)

Meiosis: 4 cells produced (daughter cells)

42
Q

What is the difference in the daughter cells produced in mitosis and meiosis?

A

Mitosis: Diploid

Meiosis: Haploid

43
Q

What is the difference in the daughter cells characteristics produced in mitosis and meiosis?

A

Mitosis: Genetically identical to each other n parent cell

Meiosis: Genetically different from each other n parent cell

44
Q

What is the difference in the cell division in mitosis and meiosis?

A

Mitosis: 1 cell division

Meiosis: 2 cell division

45
Q

What is a phenotype?

A

Observable characteristics of an organism (like eye color or blood type)

46
Q

What is a genotype?

A

combination of alleles that control each characteristic

47
Q

What’s re the 2 types of alleles?

A
  1. Dominant
  2. Recessive
48
Q

What does a dominant allele do?

A

Only needs to be inherited from one parent

49
Q

What does a recessive allele do?

A

needs to be inherited from both parents

49
Q

what is the term used to talk about if two people have 2 alleles of a gene that’s re the same?

A

Homozygous

50
Q

What are the 2 types of homozygous?

A
  1. Homozygous dominant (having 2 copies of dominant allele)
  2. Homozygous recessive (Having 2 copies of recessive allele)
51
Q

what is the term used to talk about if two alleles of a gene are different?

A

Heterozygous

52
Q

How is a dominant allele and recessive allele written?

A

Dominant: Capital letters

Recessive: Lower case

53
Q

What happens when 2 identical homozygous reproduce together?

A
  • Produce offspring with exactly the same genotype & phenotype as parents
  • pure breeding
54
Q

What happens when a heterozygous person reproduces?

A

Produce offspring with different alleles, genotypes, and phenotype than parents

Not pure breeding

55
Q

What is monohybrid inheritance?

A

Inheritance of characteristics controlled by a single gene (Mono = 1)

56
Q

How can monohybrid inheritance be determined?

A
  • Punnett Square
  • possible combination of alleles
  • ratio to be worked out
57
Q

How do u construct Punnett square?

A
  1. Determine parental genotype
  2. Select a letter (diff lower case)
  3. Split allele for each parent, add to punett Square around the outside.
  4. Fill in middle 4 squares
57
Q

What should you do when u are asked to comment on the ratio of different allele combinations?

A

Calculate a percentage chance of offspring showing specific characteristics

58
Q

What are family pedigree charts used for?

A

trace pattern of inheritance of a specific characteristic through generations of a family

59
Q

What are the following shales representative of in a pedigree chart:

  1. Square
  2. Circle
  3. Red
  4. Blue
A
  1. Square - male
  2. Circle - female
  3. Red - affected
  4. Blue - unaffected
60
Q

How do u identify an unknown genotype?

A
  • test cross
  • cross an unknown individual with recessive phenotype (genotype is homozygous recessive)
  • ratio of phenotypes in the offspring
61
Q

What is codominance?

A

Both alleles in heterozygous organisms contribute to phenotype

62
Q

What is an example of codominance?

A

inheritance

63
Q

What does I, A, B, and O represent?

A

I = gene

A, B, O = alleles

64
Q

What alleles codependent?

A

I^A and I^B are codominant but I^O is dependent

65
Q

What does I^A result in?

A

antigen A in blood

66
Q

What does I^B result in?

A

antigen B in blood

67
Q

What does I^O result in?

A

no antigens in the blood

68
Q

What are alleles on the same chromosome said to be?

A

Linked

69
Q

What do alleles control?

A
  • Particular characteristics that are found on sex chromosomes
  • sex linked
70
Q

Why are males more likely to show sex linked recessive cells?

A
  • Only have one X chromosomes
  • more likely to show sex linked recessive conditions
71
Q

Why are X alleles more prone to sex- linked recessive conditions?

A

Only alleles on the X chromosome because Y chromosome is much smaller

72
Q

What about females’ recessive sex- linked conditions?

A
  • carrier

-have 2 copies of X chromosome and are likely to inherit one dominant allele that masks effect on recessive cell

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Biology - IGCSE (19 decks)

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