Unit 2: 5 - Simple inheritance Flashcards
Why is cell division necessary?
For growth or cell repair.
What is mitosis?
A division process resulting in 2 identical cells.
What are alleles?
Each of 2 or more alternate genes for one characteristic.
What happens to chromosomes during mitosis?
They duplicate, and the new copy goes in the newly formed cell.
What are unspecialised cells?
Stem cells
When does stem cell differentiation occur in animals?
During early stages of development (in humans, as an embryo)
When does stem cell differentiation occur in plants?
Anytime throughout their lives.
Cells of offspring are produced by _____ during asexual reproduction.
Mitosis
Cells of offspring are produced by _____ during sexual reproduction.
Meiosis
What is meiosis?
When cells divide to become gametes (sperm and ova in humans)
What is the difference between gametes and normal cells?
Gametes have only one chromosome from each pair that normal cells have.
Describe the processes of meiosis.
- A copy of each chromosome is made.
- The cell now divides twice to form 4 gametes
- Each gamete has a single set of chromosomes with a different combination of genes.
Where are stem cells found in a human?
In an embryo or in adult bone marrow.
What cells do bone marrow stem cells become?
Often blood cells.
What medical uses could stem cells have?
Regrowing nerve cells to treat conditions like paralysis.
Who was the first person to suggest the idea of separately inherited ‘factors’?
Gregor Mendel.
Why were Mendel’s ideas not accepted?
Because scientists didn’t know about genes and Mendel was not in an academic position; he was a monk.
What are chromosomes made of?
DNA, a long double helix molecule.
What does DNA stand for?
Deoxyribonucleic Acid
What is a DNA fingerprint?
A unique DNA structure (apart from in identical twins) can be used to identify any individual.
How many pairs of chromosomes do human beings have?
23
What do we call an allele that is shown in the characteristics of an organism? (If there is only 1)
A dominant allele
What do we call an allele that is ‘hidden’ and is not made evident? (If there is only 1)
A recessive allele
What does homozygous mean?
When both alleles are the same (DD)
What does heterozygous mean?
When both alleles are different (Dd)
What is the phenotype?
The physical appearance of the charatceristic (e.g. dimples or no dimples)
What is the genotype?
The genetic make up - which alleles does the individual inherit? DD, Dd or dd.
What is a genetic disorder?
A disorder that is carried in the genes and passed down through generations.
What is polydactyly?
A genetic disorder where a baby is born with extra fingers or toes.
What type of allele is polydactyly?
Dominant
How many parents are needed to pass down a dominant allele?
1
What is cystic fibrosis?
A genetic disorder that affects the cell membranes and causes the production of a thick mucus that affects organs like the lungs and gut.
What type of allele is cystic fibrosis?
Recessive
How many parents are needed to create a child with a disorder which is recessive?
2
How does a child develop cystic fibrosis?
By having a recessive allele from each parent
What do we call someone who has a recessive gene for a disorder but does not have the disorder?
A carrier
What is the chance of a parent who is heterozygous for polydactyly for passing it on to the child?
50%
If both parents are heterozygous for cystic fibrosis, what is the chance of passing it on to the child?
25%
How can we show the possible outcomes of genetic crosses?
Through a Punnet square
What is the main ethical problem with embryo screening?
Many parents would want to choose a baby which does not have cystic fibrosis, which would discriminate over those who do,a swell as waste life.
What is a problem with using embryonic stem cells?
The embryos are destroyed in the process.
