Inheritance and Genetics Flashcards
Why are new cells needed in an organism? (3)
Growth, replacing worn out cells, repairing damaged tissue
Define allele?
Different form of the same gene
Define gene?
A section of DNA that codes for a particular combination of amino acids which make a specific protein
Define chromosome?
Genes grouped together
Define mitosis?
Cell division in a normal body cell, produces two identical cells
How does mitosis work?
Cell produces copies of the chromosomes in the nucleus, then divides once
Define stem cell?
Unspecialised and undifferentiated cell found in early embryos
Difference between animals and plants in terms of cellular differentiation?
Animals - differentiation only occurs in embryonic stage, so stops at maturity. Plants - cells don’t differentiate until they are in their final position in the plant, impermanent, can redifferentiate
Why is animal cloning more difficult than plant cloning?
Animal cloning - cells differentiate permanently. Plants - undifferentiated cells always produce more
What happens in meiosis?
Cell copies chromosomes so there are four sets, then divides twice in quick succession to form four gametes
Why is each gamete produced in meiosis different from the others?
They contain random mixtures of the original chromosomal pairs. Introduces variety
How is variation produced in sexual reproduction?
The combination of genes in the new pair of chromosomes contains alleles from each parent. One gamete from one parent will be different to another from the same.
How to remember mitosis and meiosis?
MITosis - Making Identical Two
MEiosis - Making Eggs (and sperm)
Difference between gametes and body cells?
Body cells have two sets of chromosomes; gametes only one
Describe the process of stem cell manufacture?
Stem cells removed from early embryo and cultured/cultivated. Stem cells differentiate into different tissues, then are implanted into a body.
Other than an embryo, where might stem cells be found?
Bone marrow, also in different tissues in the body; umbilical chords
Problems with stem cells?
Ethical (embryos can’t give permission, taking human life); may cause cancer
What does therapeutic cloning involve?
Using cells from an adult to proceed a cloned early embryo of themselves
Why didn’t people believe Mendel’s findings?
They didn’t understand genes or chromosomes
How is DNA composed?
Combinations of four different bases (ACTG) make up the long strands, grouped in threes, with each three coding for an amino acid
Define homozygous
An individual with two identical alleles for a characteristic e.g. DD or dd
Define heterozygous
An individual with different alleles for a characteristic, e.g. Dd
Define genotype
Describes the genetic makeup of an individual regarding a particular characteristic, e.g. DD or Dd
Define phenotype
The physical appearance of an individual regarding a particular characteristic, e.g. dimples or no dimples
Difference between dominant and recessive alleles?
Dominant controls the development of a characteristic when one or both chromosomes have it (one or both parents). Recessive only controls such if it is present in BOTH chromosomes (i.e. both parents)
Which gender does an XX sex chromosome determine?
Female (male is XY)
What is polydactyly?
A genetic condition where a baby is born with extra fingers or toes, caused by a dominant allele
What are the symptoms of cystic fibrosis? Is it caused by a dominant or recessive allele?
Organs are clogged by thick, sticky mucus and the reproductive system is affected, making the individual infertile in some cases
Define a carrier (of cystic fibrosis)?
Someone who has a dominant healthy allele, but also a recessive cystic fibrosis allele. They have no symptoms, but their children have a 25% chance of getting it
What are the chances of a child have polydactyly if a parent is heterozygous? And homozygous?
Heterozygous: 50% (half the gametes contain a faulty allele)
Homozygous: 100%
