Standard Grade Biology


Terms in this set (...)

What is a species?
A species is a group of living things that are so similar to one another that they are able to interbreed and produce fertile offspring.
What is variation?
No two members of a species are exactly alike. This is because variation occurs within a species. Variation occurs in the appearance of each individual.
What is discontinous variation?
In this type of variation individuals can be divided into two or more distinct groups. That means that each individual can only belong to one group or another.
What is continuous variation?
This type of variation has no distinct groups of individuals but varies in a smooth continuous way from one extreme to another.
What is the term meant by recessive?
This copy of the gene is masked by the dominant gene. This gene is only expressed if there are two copies.
What is the term meant by dominant?
This copy of the gene masks the recessive gene. This gene is always expressed.
What is a phenotype?
A phenotype is an organisms appearance, which has resulted from certain genetic information inherited from the parents is called the phenotype.
What is true breeding?
Describing an organism that on being crossed with a member of the same strain always produces more organisms of exactly the same strain.
What is the first fillial generation?
the first generation if offspring resulting from a cross.
What is the second fillial generation?
The second generation of offspring resulting from a cross where members of the F1 act as one or both of the parents.
What are chromosomes?
Chromosomes are thread like structures in the nucleus of living cells.Each normal body cell has 23 matching sets of chromosomes. Normal human cells contain 46 chromosomes. These are made up of 2 matching sets of 23. The members of a pair of chromosomes match one another, gene for gene.
What sex chromosomes determine if the baby is a girl?
What sex chromosomes determine if the baby is a boy?
Animal gametes are called:
Sperm and Eggs
Plant gametes are called:
Pollen and Ovules
What is a genotype?
A genotype is the set of genes that an organism possesses.
How many forms of each gene does a normal body cell have?
Two forms.
Where do each of those forms come from?
One from each parent
How many forms of each gene does a gamete have?
One of the two forms.
What is an allele?
Different forms of a gene
What is homozygous?
Possesses two identical forms of a gene (true breeding)
What is heterozygous?
Possesses two different forms of a gene (non true breeding)
What is mutations?
Changes in the genes of an organism can be brought about by mutations. The affected organism is said to be a mutant. Mutations can occur naturally but these are rare. Mutations can be induced by mutagentic agents which speed up the rate of mutation e.g. ultraviolet light, x-rays, tar in cigarrette smoke etc. Most mutations produce an inferior version of the original gene and are often fatal.
What is downs syndrome?
This condidtion is caused by a chromosome mutation in humans.During gamete formation the egg releases one extra chromosome and when this is fertilized by a normal sperm, the zygote has one extra chromosome. The extra chromosomes leads to an individual having the condition downs syndrome. This condition leads to impaired mental development and specific physical characteristics.
What is amniocentesis?
It is possible for doctors to carry out tests to find out if an embryo has downs syndrome or other genetic diseases. This testing uses a technique called amniocentesis, which involves collecting a sample of amniotic fluid. During pregnancy , amniotic fluid contains cells which are genetically identical to the embryo.These cells can be isolated from the amniotic fluid and the cells studied for any abnormalities. If an abnormality is present, the parents can be informed and can make decisions about whether or not to terminate the pregnancy.