inheritance,variation and evolution

• what is reproduction?


  genetic info in chromosome is passed from parents to offspring
• what is asexual reproduction?

  the production of genetically identical offspring from a single parent
• what are the differences between asexual and sexual reproduction?

  asexual:

  1 parent

  cells divide by mitosis

  no fusion of gametes

  no offspring variation

  genetically identical offspring

  
  

  sexual:

  2 parents

  cells divide by meiosis

  fertilisation of female sex cell by male

  zygote is formed->embryo->foetus

  offspring not genetically identical to parents (variation)
• what are some advantages of sexual reproduction?

  produces variation, if environment changes then variation gives a survival advantage because of natural selection, natural selection can be sped up by humans by selective breeding to increase food production
• what are the advantages of asexual reproduction?

  only one parent needed, more time and energy efficient (don't need to find a male), faster, identical offspring
• what is meiosis?


  a type of cell division that takes place in the reproductive organs to produce gametes- produces cells with 23 chromosomes
• what is the process of meiosis?

  1) cell makes copies of each chromosome (46->92)

  2) DNA replicates

  3) cell divides into 2 (each of the cells has 46)

  4)each cell divides again (now each has 23)

  now there are four daughter cells (gametes) which are not identical to eachother or parent cell
• what is a diploid?

  a cell that has 2 sets of chromosomes- in humans all cells apart from sperm and egg are diploid
• what is a haploid?


  having one set of chromosomes (as in gametes)
• what is a gamete?

  sex cell
• what is a chromosome?

  structure that DNA is packaged into
• what is a gene?


  section of DNA that is inherited and codes for one characteristic
• what is DNA?


  molecule that stores genetic information
• what is an allele?

  different forms of a gene
• what is mitosis?


  cell division of normal body cells which produces 2 identical cells
• DNA is __


  a polymer consisting of multiple nucleotide
• what does each nucleotide consist of?

  phosphate, sugar and a base
• what are the four bases?

  A, T, C, G
• what is complimentary base pairing?

  A-T, G-C
• what is a triplet?

  a sequence of 3 DNA bases that codes for a specific amino acid
• what happens to the amino acids produced by the triplet?

  will be combined into a long chain which is then folded into a protein
• what is protein synthesis?

  the process of making proteins by using the information present in the DNA
• where do the 2 stages of protein synthesis take place?

  transcription : nucleus

  translation : cytoplasm
• what is the process of protein synthesis?

  1) base sequence of gene copied into mRNA in nucleus

  2) mRNA passes into cytoplasm and attaches onto a ribosome

  3) amino acids brought to ribosome on carrier proteins

  4) ribosome reads triplet of bases on mRNA and used code to put together the amino acids in the correct order

  5) when protein chain is complete it is folded into a specific shape where it can then carry out a specific function
• what is a mutation?


  random change to base sequence of a gene
• why does a mutation occur?

  happens when chromosomes aren't replicated properly during mitosis
• what is an insertion mutation?


  where a new base is inserted into the DNA base sequence and can change amino acids
• what is a deletion mutation?


  when a random base is deleted from DNA sequence and can change way bass sequence is "read"
• what is a substitution mutation?


  when a random base in DNA base sequence is changed for a different one
• why would a gene that codes for an enzyme having a mutation make the enzyme unable to bind with its substrate?

  shape of active site changes as protein is made of different amino acids due to mutations so substrate and active site can't bind
• what does whether individual is male or female depend on?

  combination of sex chromosomes it receives (sex inheritance)
• what is heterozygous?


  different alleles for a gene
• what is homozygous?


  person has same alleles for a gene
• what is a phenotype?


  observable physical characteristics of an organism
• what is a genotype?

  alleles person has
• what is a genome?

  entire set of genetic material in an organism
• what has knowing the human genome allowed scientists to do?

  search for genes linked to diseases

  understand and treat different inherited diseases

  trace historic human migration patterns
• who is Gregor Mendel and what did he do?


  "father of genetics" He was a monk who did a lot of religious and scientific work. He worked in the mid 1800s before they knew about DNA.

  observed patterns of inheritance in pea plants in the monastery garden figured out how genes were passed down from parents
• what allele is always expressed?

  dominant allele (capital letter)
• when is a recessive allele expressed?


  when the dominant allele is absent (lowercase)