Inheritance

• What is a gamete?

  The cell with half the number of chromosomes of the parent cell
• characteristics of meiosis


  - genetic mixing happens

  - gamete production occurs

  - new cells show variation

  - two divisions occur
• Mitosis characteristics


  - new cells have same number of chromosomes as parent

  - happens in skin cells

  - two new cells are formed as a result

  - identical cells are formed
• how many chromosomes are found in an ovary cell

  46
• How many chromosomes do egg cells have?

  23
• How many chromosomes do embryo cells have?

  46
• how many chromosomes are found in a testes cell?

  46
• Name the shape which best describes the DNA polymer.

  double helix
• how is DNA organised inside the cell nucleus?

  Arranged in chromosomes
• which is larger a chromosome or a gene?

  chromosome
• What does a gene code for?

  particular sequence of amino acids
• write down the definition of the genome of a horse

  All the genetic material of the horse.
• list three reasons why it is important to understand more about the human genome
• List three reasons why it is important to understand more about the human genome.

  - To be able to identify the genes which are linked to different diseases

  
  

  - To understand and be able to treat inherited disorders

  
  

  - To use in tracing human migration patterns from the past .
• What are three advantages of sexual reproduction ?

  - Produce variation in the offspring

  
  

  - If environment changes can give a survival advantage meaning some organisms are likely to survive

  
  

  - Humans can speed up natural selection by selective breeding to increase food production
• What are three advantages of asexual reproduction ?

  - Only one one parent needed

  
  

  - More time and energy efficient as do not need to find a mate

  
  

  - Faster than sexual reproduction

  
  

  - Many identical offspring can be produced when conditions are favourable
• List three organisms which reproduce using both sexual and asexual parasites

  - Malarial parasites

  - Fungi

  - Strawberry plants

  - Daffodils
• Where would you find a nucleotide ?

  DNA
• What does a nucleotide consist of?

  - Common sugar

  - phosphate group

  - base
• What are the symbols of the 4 bases found in DNA?

  A T C G
• What does the code for an amino acid consist of?

  A sequence of three bases
• Fill in the missing terms:

  
  

  The long strands of DNA are made of alternating ________ and __________ sections.

  
  

  Attached to each ________ is one of the four bases.

  
  

  The DNA polymer is made up of repeating _____ units .

  - sugar

  - phospahte

  - sugar

  - nucleotide
• In the complementary strands of DNA - which base is T always linked to?

  A
• Which organelle in the cytoplasm carries out protein synthesis?

  Ribosome
• What do carrier molecules bring to the organelle from the cytoplasm?

  Amino acids
• What happens in protein synthesis once the protein chain is complete?

  The protein folds up into a unique shape
• What happens if a mutation codes for a slightly altered enzyme protein with a different shape?

  The enzyme may no longer fit the substrate binding site
• What can non-coding parts of DNA do?

  Switch genes on or off and affect how genes are expressed
• What are the different forms of a gene called ?

  Alleles
• Why is it easy to describe an organisms phenotype for a particular characteristic but very difficult to state the genotype?

  Most characteristics are a result of multiple genes interacting
• If two heterozygous tall plants were crossed 75 times , what proportion of the offspring would you expect to be short?

  What is polydactyly and is it caused by inheriting a recessive or dominant allele?
• What is polydactyly and is it caused by inheriting a recessive or dominant allele?

  A genetic disorder which results in having extra fingers or toes - dominant allele
• Is someone who is heterozygous for cystic fibrosis healthy ?

  Yes , they are a carrier but do not suffer from CF themselves
• Many people feel opposed to the screening of embryos to identify the CF allele. Suggest two reasons why they may feel this way.


  - Screening procedure may cause miscarriage or damage embryo / fetus. The embryo has a right to live

  
  

  - Screening is expensive and could be used for other purposes

  
  

  - Have to make moral / ethical or religious decisions as a result such as whether to terminate .
• The flower colour for pea plants is controlled by a single gene . Red flowers are dominant to white flowers.

  
  

  A homozygous dominant plant and a heterozygous plant are crossed to produce offspring.

  
  

  Let R represent the dominant allele.

  
  

  What is the phenotype of the homozygous dominant plant ?

  Red flowers
• What does variation mean?

  Variation means the differences in the characteristics of individuals in a population
• Write a definition for evolution

  A change in the inherited characteristics of a population over time, through a process of natural selection.
• What does the theory of evolution by natural selection state?

  All species of living things have evolved from simple life forms that first developed more than 3 billion years ago
• What is the definition of the term species?

  A group of similar looking individuals who can breed together and produce fertile offspring.
• Humans choose animals or plants to breed from based on usefulness or appearance.

  List four characteristics which would be selected

  (two in plants and two in animals)

  - Disease resistance in crop plants

  - Animals which produce more meat or milk

  - Domestic dogs with a gentle nature

  - Large or unusual flowers