Biology 3 voice of the genome

• Eukaryotic cells contain what?

  Nucleus and membrane bound organelles
• Features of the nucleus


  -Double membrane (envelope)

  -Contain DNA wrapped in histones

  -Nucleolus (site of ribosome production)
• What is the rough Endoplasmic reticulum and its function?

  -Flattened sacs enclosed by a membrane with ribosomes on the surface

  -RER folds and processes proteins made on the ribosome
• What is the smooth Endoplasmic reticulum and its function?

  -A series of membrane sacs

  -It produces and processes lipids and steroids
• What is the Golgi apparatus and its function?

  -Series of flattened sacs

  -modify, package, sort and transport cellular products
• What are mitochondria and its function?


  -Bound by a double membrane (envelope)

  -The inner membrane is folded to form projections called cristae

  -inner matrix contains enzymes needed for cellular respiration
• What are centrioles and its function?

  -Hollow cylinders

  -involved in cell division
• 80s ribosomes are?

  Composed of 2 subunits

  -site of protein synthesis
• Lysosome function and structure

  -vesicles

  -containing digestive enzymes bound by a single membrane
• What is protein trafficking

  -Proteins are produced on ribosomes

  -The are then folded by the RER

  -Then transported to the Golgi apparatus in vesicles

  -Modified in the Golgi

  -Golgi packages proteins into vesicles and they can then be transported around the cell or leave by exocytosis.
• Prokaryotic cell structure:

  Cell wall

  -Rigid made of peptidoglycan.

  -Provides the cell with strength and support
• Prokaryotic cell structure:

  Slime capsule

  Protective slimy layer

  -helps to retain moisture
• What is plasmid DNA?

  Small loops of DNA
• Prokaryotic cell structure:

  Flagellum

  Tail like structure which rotates to move the cell.
• Prokaryotic cell structure:

  Pili

  Hair like structures which attach to other bacterial cells
• Prokaryotic cell structure:

  70s ribosomes


  -Composed of 3 subunits

  - The site of protein synthesis
• What is an ovum and what is its function?

  -Contains the zona pellucida which is a protective coating. It hardens after sperm have entered to prevent polyspermy

  -Contains haploid nucleus so

  -Cortical granules release substances causing the zona pellucida to harden

  -follicle cells form a protective coating around the egg
• What is spermatozoa and what is its function?

  -Contains many mitochondria to provide energy for the flagellum to move

  -Acrosomes contain digestive enzymes which break down the zona pellucida allowing the sperm to penetrate the egg
• Fertilisation steps

  1) The sperm head meets the zona pellucida causing an acrosome reaction

  2)Sperm head fuses with the cell membrane allowing sperm to enter the egg

  3) Cortical reaction hardens to zona pellucida to prevent polyspermy

  4) The nuclei fuse and a full set of chromosomes is formed forming a diploid zygote
• What is the locus of a gene?

  position of a gene on a chromosome
• Gene factors to do with position (sec linked)

  -Some genes are sex linked as they occur on the x chromosome

  -Some genetic conditions are sex linked as in men if there is a faulty copy of a gene on an x chromosome there isn't a backup.
• Stages of the cell cycle in mitosis


  interphase, prophase, metaphase, anaphase, telophase, cytokinesis
• Stages of the cell cycle in mitosis within interphase


  G1- cell grows and DNA replicates

  S-Chromosomes are replicated and condense to form chromatin

  G2- the cell prepares to divide replicating organelles.
• What is meiosis

  -A form of cell division that gives rise to genetic variation.

  -Produces haploid gametes
• How is genetic variation achieved?


  -Crossing over= the exchange of sections of DNA between homologous chromosomes

  -Independent assortment= there are various ways in which paternal chromosomes can be distributed across the daughter cells
• What are stem cells?

  Undifferentiated cells that can keep dividing to give rise to other types of cells
• What are multipotent cells?

  Cells that can give rise to different types of cells
• What are pluripotent cells?


  can give rise to many different types of specialised cells but not placental cells
• What are Totipotent cells?

  Can give rise to all specialised types of cells
• What are sources of stem cells

  -Embryonic stem cells or adult stem cells (from bone marrow)
• What are some uses for stem cells?

  Can replace damaged tissue
• Ethical issues of stem cells?

  Embryos are killed in the process of getting stem cells.

  Cells could also become cancerous when transplanted
• How do cells become specialised?

  -A stimulus acts on unspecialised cells

  -Activator and repressor molecules bind to promoter regions on the DNA sequence. Some genes are switched on or off.

  -The active genes are transcribed to produce RNA

  -mRNA is then translated on ribosomes and used to produce protein

  -The protein has the ability to change the structure and function of cells.
• What is the Phenotype?


  The characteristics of an organism which results from the interaction between the genes of the organism with the environment in which it lives.
• What are the two types of variation in the phenotype?


  Continuous= Within a range and it includes mass and height

  Discontinuous= Only tales particular values like gender and shoe size.
• What are characteristics only affected by one gene called?

  Monogenic
• What are characteristics that are affected by multiple genes at different loci called?

  Polygenic inheritance which often gives rise to continuous variation
• What are characteristics that are influenced by both genotype and the environment

  -Height

  -Some people are more genetically predisposed to cancer due to oncogenes which through smoking can be exposed to chemicals leading to uncontrolled cell division

  -Animal hair colour tyrosinase darkens fur and is only active below 31 degrees hence the extremities of Siamese cats are dark
• What are epigenetic modifications?

  Epigenetic modifications change the activation of certain genes.
• What is DNA methylation?

  DNA methylation is the addition of methyl groups. Acting to supress gene transcription. This is a permanent change preventing a cell from converting back to a stem cell.