Unit 4

• classification hierarchy:

  Domain

  Kingdom

  Phylum

  Class

  Order

  Family

  Genus

  Species
• importance of courtship behaviour:

  To ensure successful reproduction

  - enables them to recognise own species and opposite sex

  Synchronises mating behaviour - indicates sexually mature and in season (releasing egg)

  
  

  To ensure the survival of the offspring

  - Form a pair bond

  - Choose a strong and healthy mate
• What are some aseptic techniques you need to use when working with microbial cultures:

  
  

  - regularly disinfect surfaces

  - use sterile equipment

  - work near a Bunsen burner - draws away any microbes in air

  - minimise time spent with lid off the agar plate - stops airborne microbes contaminating culture
• process of meiosis:

  1. DNA unravels & replicates so there are 2 copies of each chromosome

  2. DNA condenses to form double-armed chromosomes made from 2 sister chromatids, joined together by a centromere

  3. first division - the chromosomes arrange themselves into homologous pairs

  4. homologous pairs separate to halve the chromosome number

  5. second division - pairs of sister chromatids are separated

  6. four haploid cells that are genetically different are produced
• independent segregation:

  - 4 daughter cells have completely different combination of maternal & paternal chromosomes

  - due to random separation of homologous pairs in 1st division
• chromosome non-disjunction:

  • When chromosomes fail to separate correctly in meiosis, resulting in gametes with one more or less chromosome than normal.
• genetic bottleneck:

  - event that causes large decrease in population

  - reduces number of different alleles in gene pool = reduces genetic diversity
• founder effect:

  - type of genetic bottleneck

  - when a few organisms from population start a new colony, there's only a small number of diff alleles in new gene pool

  - might lead to higher incidence of genetic disease if a previously rare allele = more common
• What is directional selection:

  
  

  • Occurs when environmental conditions change.
  • Individuals with phenotypes suited to the new conditions will survive and pass on their genes.
  • Over time the mean of the population will move towards these characteristics
• stabilising selection:

  • Occurs when environmental conditions stay the same. Individuals closest to the mean are favoured, and any new characteristics are selected against.
  • Results in low diversity.
• natural selection:

  
  

  - random mutations result in new alleles

  - some alleles provide an advantage, making an individual more likely to survive and reproduce.

  - their offspring receive the new allele, and frequency continues to increase over many generations
• suggest advantages of mRNA rather than DNA for translation:

  
  

  - shorter and contains uracil = breaks down quickly so no excess polypeptide forms

  - single-stranded and linear = ribosome moves along strand and tRNA binds to exposed bases

  - contains no introns
• Transcription:

  • Hydrogen bonds between DNA bases break
  • Only one DNA strand act as a template
  • Free adjacent RNA nucleotides align by complementary base pairing
  • In RNA, Uracil is used instead of thymine
  • RNA polymerase joins RNA nucleotides together by phosphodiester bonds from pre-mRNA
  • pre-mRNA is spliced to remove introns, forming mRNA
• translation:

  1. mRNA attaches to ribosomes
  2. tRNA anticodons bind to complementary mRNA codons
  3. tRNA brings a specific amino acid.
  4. Amino acids join by peptide bonds.
  5. Amino acids join together with the use of ATP
  6. tRNA released after amino acid joined to the polypeptide
  7. The ribosome moves along the mRNA to form the polypeptide;
• Meaning of degenerate

  -More than one codon codes for a single amino acid
• Describe how mRNA is produced in the nucleus of a cell.

  • Helicase Breaks hydrogen bonds;
  • Only one DNA strand acts as template
  • RNA nucleotides attracted to exposed bases
  • Attraction according to base pairing rule
  • RNA polymerase joins (RNA) nucleotides together
• Describe and explain the processes that occur during meiosis that increase genetic variation

  
  

  1. Homologous chromosomes pair up

  2. Independent segregation

  3. Maternal and paternal chromosomes are re-shuffled in any combination

  4. Crossing over leads to exchange of parts of non-sister chromatids

  5. creating new combinations of alleles
• Explain how the chromosome number is halved during meiosis

  • Homologous chromosomes (pair)
  • One of each pair goes to each (daughter) cell
• Describe the process of crossing over and explain how it increases genetic diversity

  
  

  • Homologous pairs of chromosomes form a bivalent;
  • Chiasma form
  • equal lengths of non-sister chromatids are exchanged
  • Producing new combinations of alleles

  -Increases genetic diversity as chromosomes can swap different genes so that they are genetically different to their parents.

  -Reduces the chances of interbreeding which can lead to mutations
• meaning of non-overlapping

  -each triplet is only read once
• What is the genome?

  
  

  The complete set of genetic information contained in the cells of an organism.
• translation

  1. mRNA attaches to ribosomes
  2. tRNA anticodons bind to complementary mRNA codons
  3. tRNA brings a specific amino acid.
  4. Amino acids join by peptide bonds.
  5. Amino acids join together with the use of ATP
  6. tRNA released after amino acid joined to the polypeptide
  7. The ribosome moves along the mRNA to form the polypeptide;
• Transcription:

  • Hydrogen bonds between DNA bases break
  • Only one DNA strand act as a template
  • Free adjacent RNA nucleotides align by complementary base pairing
  • In RNA, Uracil is used instead of thymine
  • RNA polymerase joins RNA nucleotides together by phosphodiester bonds from pre-mRNA
  • pre-mRNA is spliced to remove introns, forming mRNA
• suggest advantages of mRNA rather than DNA for translation:

  
  

  - shorter and contains uracil = breaks down quickly so no excess polypeptide forms

  - single-stranded and linear = ribosome moves along strand and tRNA binds to exposed bases

  - contains no introns
• process of meiosis:

  1. DNA unravels & replicates so there are 2 copies of each chromosome

  2. DNA condenses to form double-armed chromosomes made from 2 sister chromatids, joined together by a centromere

  3. first division - the chromosomes arrange themselves into homologous pairs

  4. homologous pairs separate to halve the chromosome number

  5. second division - pairs of sister chromatids are separated

  6. four haploid cells that are genetically different are produced
• crossing over of chromosomes:

  
  

  • homologous pairs of chromosomes associate to form bivalents
  • chiasma forms
  • equal lengths of non-sister chromatids are exchanged
  • producing new combination of alleles
• Define a niche

  -The role of a species within its

  environment.

  -Species sharing the same

  niche will compete with each other
• three types of adaptation?

  Give examples of each

  
  

  -Anatomical (changes to body structure) e.g. oily

  fur.

  ● Physiological (changes to bodily processes) e.g.

  venom production.

  ● Behavioural (changes to actions) e.g. hibernation
• Describe the role of a ribsome in the production of a polypeptide

  • mRNA binds to ribosome- 2 codon binding sites
  • tRNA with anticodons to bind
  • Catalyses formation of peptide bond between amino acids
  • Ribosome moves along mRNA to form polypeptide
• a species is a group of organisms that can successfully interbreed and produce fertile offspring
• Process of natural selection

  • Random genetic mutation of DNA results in new alleles and variation
  • Selection pressure (new competition, environmental change, loss of habitat)
  • Individuals with beneficial/ advantageous phenotypes survive
  • Individuals successfully reproduce and pass on beneficial allele
  • Frequency of beneficial allele increases and individuals with advantageous phenotype increases
  • chance of survival increases
• community

  all the different species that live in an area and interact with each other
• Random sampling

  • Grid the area
  • Set up coordinates using a square
  • Random number generator to give coordinates
  • Repeat at least 10 times of each quadrat
  • Calculate percentage cover/ mean/ do a stats test
• biodiversity

  variety of living organisms in an area
• community

  • all the populations of different species in an habitat
• species richness

  • number of different species in a community
• population:

  • all of the organisms of the same species that live in the same place
• index of diversity

  N= Total number of organisms of all species

  n= Total number of organisms of one species

  
  

  d =

  N(N- 1)

  ——————-—

  En(n - 1)
• genetic variation:

  -Random fertilisation

  -Results in a new combination of alleles
• useful to calculate index of diversity over species richness as ......

  IOD: measures the number of each species

  more useful as be lots of one particular species