SB3

• What process are gametes produced by?

  Meiosis
• What type of cell is a gamete?

  Haploid, 23 chromosomes
• What happens at fertilisation?

  A male gamete fuses with a female gamete to produce a zygote (fertilised egg) the zygote ends up with a full set of chromosomes, diploid
• How does a zygote develop into an embryo?

  It undergoes cell division
• What are the disadvantages of asexual reproduction?

  No genetic variation between offspring in the population, if there was an unfavourable change in environment, the whole population would be affected
• What are the disadvantages of sexual reproduction?

  It takes more time and energy and so produce fewer offspring overtime

  2 parents are needed so there are issues if individuals are isolated
• What is DNA?

  Polymers made up of lots of repeating units called nucleotides
• What does a nucleotide consist of?

  A sugar, a phosphate group, and 1 base
• What is produced at the end of meiosis?

  4 haploid daughter cells, genetically different
• Where does meiosis occur in humans?

  Reproductive organs
• What are the advantages of asexual reproduction?

  Produces lots of offspring quickly as the reproductive cycle is fast

  Only 1 parent is needed, which is more efficient than waiting for a mate
• What are the advantages of sexual reproduction?

  Creates genetic variation within the population, meaning different individuals have different characteristics leading to natural selection and evolution
• What do the sugar and phosphate groups in the nucleotides form?

  A “backbone“ to the DNA strands. The sugar and phosphate groups alternate
• One of 4 different bases join to each sugar, what are the bases?

  A (adenine) T (thymine) C (cytosine) G (guanine)
• What is the structure of DNA?

  A DNA molecule has two strands coiled together, in the shape of a double helix
• What are the complementary base pairs joined together by?

  Weak hydrogen bonds
• What is a chromosome?

  Long, coiled up molecules of DNA
• Where are chromosomes found?

  In the nucleus of a eukaryotic cell
• What is a gene?

  A section of DNA on a chromosome that codes for a particular protein
• What is a genome?

  All of an organisms DNA
• Do you want DNA extraction from fruit, why is the fruit put in a beaker with detergent and salt?

  The detergent makes the cell membranes break down and release DNA

  The salt makes the DNA stick together
• In the second stage of DNA extraction why do you filter the mixture?

  To get the froth and big, insoluble bits of cell out
• in DNA extraction, what liquid is added to the filtered mixture?

  Ice cold alcohol
• Why does the DNA start to come out during DNA extraction?

  DNA isn’t soluble in cold alcohol and will appear as a stringy white precipitate that can be fished out on a glass rod
• What are proteins made up of?

  chains of molecules called amino acids
• Each different protein has its own particular what?

  number and order of amino acids
• Why do the amino acids chains fold up?

  To give each protein a different, specific shape which means each protein can have a different function
• What decides the order of amino acids in a protein?

  The order of the bases in a gene
• What is a base triplet?

  Each amino acid is coded for by a sequence of 3 bases in the gene
• Why does each gene contain a different sequence of bases?

  Allows it to code for a particular protein
• What is non-coding DNA?

  DNA that doesn’t code for any amino acids
• What is a mutation?

  A rare random change to organisms DNA base sequence that can be inherited
• How does a mutation affect a protein?

  If a mutation occurs in a gene, it produces a genetic variant. the genetic variant may code for a different sequence of amino acids, which may change the shape and activity
• What might happen to the activity of an enzyme?

  Increase, decrease, or stop altogether
• Where are proteins made?

  In the cell cytoplasm by subcellular structures called ribosomes
• Where is DNA found?

  In the cell nucleus and can’t move out of it because it’s really big. the cell needs to get the information from the DNA to the ribosome in the cytoplasm
• How is DNA different mRNA?

  Like DNA mRNA is a polymer of nucleotides but it’s shorter and only a single strand. it uses U (uracil) instead of T (thymine)
• What is the RNA polymerase?

  The enzyme involved in joining together RNA nucleotides to make mRNA. this stage of protein synthesis is called transcription
• What is the 1st stage of transcription?

  RNA polymerase binds to a region of non-coding DNA in front of the gene
• What is the 2nd stage of transcription?

  The two DNA strands unzip and the RNA polymerase moves along 1 of the strands of DNA