B2.7 - Cell Division and Inheritance Flashcards
How are chromosomes in body cells found?
In pairs.
Do body cells divide by mitosis or meiosis?
Mitosis.
What do chromosomes contain?
Genetic Information.
What happens when a cell divides by mitosis?
- copies of the genetic material are made
- then the cell divides once to form two genetically identical body cells.
When does mitosis occur?
During growth or to replace cells.
How many sets of chromosomes do body cells have?
Two.
How many set of chromosomes do gametes have?
One.
What type of cell division forms gametes?
Meiosis.
What happens during meiosis?
-copies of the genetic information are made
-then the cell divides twice to form four
gametes, each with a single set of
chromosomes.
What happens when gametes join in fertilisation?
A single body cell with new pairs of chromosomes is formed.
How does a new person develop from fertilisation?
The cell formed by fertilisation divides by mitosis.
How is differentiation different for plants and animals?
Most types of animal cells differentiate at an early stage whereas many plant cells retain the ability to differentiate throughout life.
What is cell division restricted to in mature animals?
Repair and replacement.
What are stem cells?
Cells from human embryos or adult bone marrow.
How can stem cells be used?
They can be made to differentiate into many different types of cell, eg nerve cells.
What can stem cells develop into?
Any kind of human cell.
How can stem cells help with certain conditions?
They may be able to help conditions such as paralysis.
How are offspring produced by asexual reproduction?
They are produced by mitosis from the parental cells. The offspring then have the same alleles as the parents.
What is an allele?
Different forms of the same gene, eg blue eyes or brown eyes.
What is a chromosome?
A structure of nucleic acids and protein found in the nucleus, carrying genetic information.
What is a genotype?
The entire set of genes in an organism.
What is a gene?
A small section of DNA.
What does hetrozygous mean?
A person is heterozygous for a certain gene if they have two different alleles., eg one blue eye allele and one brown eye allele.
What does homozygous mean?
An individual is homozygous for a certain gene if they have two identical alleles, eg two brown eye alleles.
What is a phenotype?
The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.
Why does sexual reproduction give rise to variation?
When gametes fuse, one of each pair of alleles comes from each parent.
How is the sex of the offspring determined by sexual reproduction?
One of the 23 pairs of chromosomes carries the genes that determine sex. In females the sex chromosomes are the same (XX) in males the sex chromosomes are
different (XY).
What is a dominant allele?
An allele that controls the development of a characteristic when it is present on only one of the chromosomes.
What is a recessive allele?
An allele that controls the development of characteristics only if the dominant allele is not present.
What are chromosomes made up of?
Large molecules of DNA (deoxyribo nucleic acid) which has a double helix structure.
What do genes do?
Each gene codes for a particular combination
of amino acids which make a specific protein.
How an people be identified by their DNA?
Each person (apart from identical twins) has unique DNA. This can be used to identify individuals by DNA fingerprinting.
What is Polydactyly, and how is it caused?
Having extra fingers or toes – is caused
by a dominant allele of a gene and can therefore
be passed on by only one parent who has the disorder.
What is Cystic Fibrosis and how is it caused?
A disorder of cell membranes. It must be inherited from both parents, who may be carriers of the disorder without actually having it. It is caused by a recessive
allele of a gene, therefore if two carriers have a child, it will potentially have Cystic Fibrosis.
How can genetic disorders be caught early?
Embryos can be screened for certain alleles.
