All Flashcards
Identify and describe the events of the cell cycle (animal and plant cell).
-Cell cycle is the serious events that cells go through as they grow and divide.
3 phases of interphase
G1: cell increases in size and synthesizes new proteins and organelles.
S: proteins associated with DNA are also synthesized.
G2: Organelles and molecules required for cell division are produced.
4 phases of mitosis
Prophase: chromosomes become visible and centrioles take up position on the opposite sides of the nucleus
Metaphase: chromosomes line up across the center of the cell
Anaphase: chromosome move until they form 3 groups near the poles of spindle.
Telophase: nuclear envelope reforms around each group of chromosomes and mitosis are complete but cytokinesis is not.
What are chromosomes and why is it so important to maintain the number of chromosomes during cell division?
Chromosomes are made up of DNA and proteins and are only visible during cell division.
If there are too many or too few chromosomes, inside a cell, then there will be a corresponding increase or decrease in the number of proteins that are made. This probably causes cell stress and leads to cellular damage.
How is cell division controlled (how is it regulated)?
Controlled by cyclins, internal regulators and external regulators.
What is the link between mitosis and cancer?
Cancer is essentially a disease of mitosis. The normal ‘checkpoints’ regulating mitosis are ignored or overridden by the cancer cell. Cancer begins when a single cell is transformed or converted from a normal cell to a cancer cell.
Describe, in detail, the stages of meiosis and cytokinesis.
Mitosis
The process of reduction division in which the number of chromosomes per cell is cut in half chromosomes in a diploid cell.
Process made up of: Interphase + Meiosis l + Meiosis ll
Cytokinesis
Cytokinesis in plants is different with the development of the cell plate which becomes a separating membrane and eventually a cell wall
This is M phase
Explain why it is important to reduce the number of chromosomes.
Because meiosis creates cells that are destined to become gametes, this reduction in chromosome number is critical. Without it, the union of two gametes during fertilization would result in offspring with twice the normal number of chromosomes.
Describe crossing-over and why it is important.
Crossing over is a cellular process that happens during meiosis when chromosomes of the same type are lined up.
Homologous chromosomes exchange alleles/genes to produce new chromosomes.
Describe nondisjunction in human chromosomes and the conditions that it may cause (Down’s syndrome, Turner syndrome etc.)
An individual may be born with three copies of a chromosome. This is called trisomy. The most common form of trisomy is Downs Syndrome. Downs Syndrome results from an extra copy of chromosome 21. It reduces mild to severe mental retardation and increases the susceptibility to many diseases and higher frequency of some birth defects.
Be able to identify a normal karyotype vs. an abnormal one.
What are the main scientific discoveries that led to the knowledge of structure, function and replications of DNA. (Griffith, Avery, Hershey-Chase)
Griffith
Genetic information could be transferred from one bacteria to another, he called this process of transformation.
Avery
The DNA stores and transmits the genetic information from generation of an organism to the next.
Hershey-Chase
DNA is genetic material.
Describe the Watson and Crick double helix model of DNA
Twisted ladder
Held together with hydrogen bonds but only between certain NB
The hydrogen bonds are weak but just strong enough to hold the ladder together
This rule is called base pairing
Explain DNA replication. (Don’t forget about Chargaff’s rule of base pairing)
The two strands have separated allowing two replication forks to form. As each new strand is formed, new bases are added following the rules of base pairing which is the principle explained by Chargaff’s rules: adenine (A) always bonds with thymine (T) and cytosine (C) always bonds with guanine (G).
Compare and contrast the structure of DNA and tRNA, mRNA and rRNA and explain their role in protein synthesis.
DNA and tRNA
DNA are wrapped around histones but tRNA has a specific amino acid attached.
mRNA and rRNA
mRNA molecules carry the coding sequences for protein synthesis and are called transcripts but rRNA molecules form the core of a cell’s ribosomes.
Explain the process of transcription and translation..
Transcription
The process in which the DNA sequence of a gene is transcribed to make an RNA molecule.
Translation
Take place in the ribosome.
During translation, the cell uses information from mRNA to produce proteins.
Explain what is a gene mutation and how it can protein synthesis.
Gene mutation changes in a single gene
The ribosome won’t read the correct amino acid.
Explain how protein synthesis comes into play in cystic fibrosis and sickle cell anemia.
When protein isn’t present in the membrane as it should be, then it cannot be transported to the cell membrane. So the cells in the person’s airway and lung are unable to transport chloride ions as long as a result the airways become clogged with thick mucus. Therefore, their lungs don’t function properly. Just because of that missing amino acid.
Describe the life and work of Gregor Mendel and how his studies led to the beginning of the understanding of the inheritance of genes.
Mendel was a monk who studied science and mathematics. He spent 14 years teaching high school and working in a monastery where he was in charge of the garden.
The crux of his works consisted of the study of pea plants.
He concluded that Biological inheritance is determined by factors that are passed from one generation to the next, and the Principle of Dominance states that some alleles are dominant and others are recessive.
Understand and describe independent assortment, complete/incomplete dominance, codominance, multiple alleles and polygenic traits.
Independent assortment
One allele is not completely dominant over another
The heterozygous phenotypes are somewhere in between the two homozygous phenotypes
E.g. flower colour in four o’clock plants
Codominance
Both allele contribute to the phenotype of the organism
E.g. black and white feather colour in certain varieties of chickens
Multiple alleles
Genes have more than two alleles
E.g. blood types in humans and eye colour in humans
Polygenic traits
Two or more genes control a trait
E.g. skin colour in humans
Predict the outcome of monohybrid and dihybrid crosses using genotype and phenotype ratios.
Know what the theory of evolution is.
A collection of scientific facts, observations, and hypotheses which states that modern organisms have descended from ancient organisms.
Describe Darwin’s voyage and what he observed.
He travelled all over the world, to places that people had never been before. Then he saw a whole bunch of different animals, plants and fossils, he also collected samples from all over.
He observed the patterns of diversity in which plants and animals were well suited to whatever environment they lived in.
Discuss that ideas and scientists who shaped Darwin’s thinking (Hutton, Lyell, Lamarck and Malthus)
Hutton
Proposed that the earth is shaped by geological forces that took place over extremely long periods of time.
Estimated that the earth is millions, not thousands of years old.
Lyell
Explains that processes occurring now have shaped Earth’s geological features over long period of time.
Lamarck
Published his hypotheses of the inheritance of acquired traits.
Explains how organism changes over time.
Malthus
Predicted that the human population will grow faster than the space and food supplies needed to sustain it.
Discuss the weaknesses of Darwin’s theory.
Scientific advances in many fields of biology have confirmed and expanded most of Darwin’s hypothesis but the evolutionary theory continues to change as new data are gathered and new ways of thinking arise.
Still much debate on how new species arise and why species become extinct.
There is also uncertainty about how life began.
Describe and give an example of homeostasis.
The process by which organisms keep internal conditions relatively constant despite changes in the external environments.
Non-living examples: Heating system of a house is controlled by feedback inhibition.
Living examples: Body temperature control in humans
Explain feedback inhibition.
Process in which a stimulus produces a response that opposes the original stimulus.
