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Biology S3


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[Front]


What does cytosine always bond with?
[Back]


guamine

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173 questions
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What is a species?
A group of organisms so similar that they can interbreed to produce fertile offspring.
What happens if different species interbreed?
It is possible that a hybrid could be produced
Why are hybrids usually sterile?
Due to the number of chromosomes they have
What are some examples of hybids?
Zorse (zebra and horse), cama (camel and llama), liger (lion and tiger)
What is variation?
All the differences which exist between members of the same species
What is discrete variation?
A characteristic that can be used to divide up the members of the population into distinct groups
What are some examples of discrete variation?
Eye colour, blood type, fingerprint type, hair colour
What is continuous variation?
A characteristic that varies from one extreme to the other and does not fall into distinct groups
Where is genetic information stored?
On chromosomes in the nucleus
What is meant by characteristics?
The appearance of the organism
Where does genetic information come from?
Gametes, one set comes from the male and one set comes from the female
What does haploid mean?
One set of information
What does diploid mean?
Two sets of information
What is a zygote?
A cell formed by a fertilisation event between two gametes
What happens after about 5 days from fertilisation?
It becomes a blastocyst which implants itself in the uterus?
What is the placenta?
The organ that provides oxygen and food from the mother for the growth of the fetus.
What is the uterus?
The muscular organ where the fetus grows and develops.
What is the umbilical cord?
A cord connecting the baby to the placenta
What is the amniotic sac?
A bag of watery fluid
What is amniotic fluid?
Watery fluid protecting the developing fetus.
What is the cervix?
The neck of the uterus
What is the vagina?
Another name for the birth canal
What are the four teratogen groups?
Chemical agents, infectious agents, physical agents and maternal conditions?
What is an example of a chemical teratogen?
Thalidomide - a medication that was used for morning sickness (causes birth defects, many of the babies died within the first year of life) Recreational drugs (reduces blood flow to fetus, miscarriages, bleeding and deaths)
What is an example of an infectious teratogen?
Mumps (a viral disease)- causes miscarriages. Listeria (a bacterial disease)- causes miscarriages, premature birth, infection to the newborn
What is an example of a physical teratogen?
Radiation - causes mutations and deaths, defects can be passed on to the next generation. Mechanical Forces - causes hip dislocation and deformaties
What is an example of a maternal condition teratogen?
Lack of something in diet (for example, iron) - can cause anaemia and stillbirths
Why are chromosomes arranged in pairs?
One comes from the mother and one from the father
What are some characteristics of someone with Down's Syndrome?
Slanting eyes, flattened nose, protruding tongue, thickening of hands and feet and learning difficulties
What is different about someone with Down's Syndrome?
The have an extra chromosome in the 21st set.
What is a mutation?
A change in the number or structure of chromosomes
Why is Down's Syndrome a mutation?
It's a change in the number of chromosomes
What are genes?
Sections of chromosomes
What do genes code for?
Different characteristics
Why do cells contain two copies of the each gene?
One from the mother, one from the father
Each chromosome is a molecule of what?
Tightly coiled deoxyribonucleic acid
What do DNA bases do?
Hold the genetic code
What does the age of the mother affect children with Down's Syndrome?
The older the mother, the more common Down's Syndrome is
What is the nucleus?
The control centre to co-ordinate the cells activities
What is each stand of DNA made from?
Repeated units called bases
What are proteins made from?
Repeating units called amino acids
What are some ways to speed up a reaction?
Heat it, stir it, increase concentration, smaller particle size, increase pressure
How would you make hydrogen peroxide speed up it's reaction?
Add manganese dioxide or crushed grape cells
What is a catalyst?
A chemical used to speed up a reaction but is itself not used up.
What is an enzyme?
A biological catalyst
Why are enzymes required?
To speed up biological reactions without making them go too fast. They keep us alive.
What does it mean by enzymes are specific?
Enzymes are different and do different jobs
What is a degradation reaction?
A breaking down reaction
What is a synthesis reaction?
A building up reaction
Describe what happens in a degradation reaction?
An enzyme takes a substrate in and makes an enzyme-substrate complex. At the end, you have an unchanged enzyme and the products
Describe what happens in a synthesis reaction?
An enzyme takes in substrates and makes an enzyme-substrate complex. At the end, you have the unchanged enzyme and a product.
How are enzymes specific?
Enzymes fit only one type of substrate therefore they can only catalyse one reaction
Where are the instructions for making enzymes kept?
In the DNA in the form of genes in the nucleus
What is the active site?
The part of the enzyme that fits the shape of the substrate
What is the substrate and products of catalase?
Hydrogen peroxide, water and oxygen
What is the substrate and products of pepsin?
Protein, peptides then amino acids
What is the substrate and products of trypsin?
Protein, peptides and amino acids
What is different about phosphorylase compared to enzymes like catalase, amylase and pepsin?
Phosphorylase is a synthesis reaction - meaning it takes something small and builds it up rather than taking something big and braking it down
Describe how phosphorylase works in the growing of potatoes?
Potato plant leaves photosynthesise to create sugars, these sugars are transported to the roots, phosphorylase then turns the sugars into starchy potatoes
What does boiling a leaf do?
It kills the leaf and stops it photosynthesising
What is horticulture?
Cultivation of plants in gardens, greenhouses and on farms
What does leaving a leaf in ethanol do?
Removes the green colour (chlorophyll)
What is horticulture?
Cultivation of plants in gardens, greenhouses and on farms
What is horticulture?
Cultivation of plants in gardens, greenhouses and on farms
What does adding iodine to a leaf do?
Lets us see if the leaf contains starch
What is horticulture?
Cultivation of plants in gardens, greenhouses and on farms
What is photosynthesis?
The process by which green plants use carbon dioxide from the air and water from the soil to produce sugar and oxygen gas
What is horticulture?
Cultivation of plants in gardens, greenhouses and on farms