B2.5 Simple inheritance in animals and plants Flashcards
Why do cells need to divide?
to replace lost cells (damaged or worn out) and make more cells for other purposes
What is a gene?
a section of DNA that controls a characteristic or part of a characteristic, it contains instructions to make a specific protein
What is an allele?
different forms of the same gene
What are genes grouped together into?
chromosomes
How many chromosomes does a human have in the nucleus of its body cells?
46 chromosomes in 23 pairs
one of each pair is from mother and one from father
What is different about chromosomes in gametes?
sex cells contain only one of each pair of chromosomes
What are the two types of cell division called?
Mitosis and Meiosis
What is Mitosis?
asexual reproduction-produces two identical cells with same genetic info. no genetic variation
plants and animals use this for growth and repair
asexual reproduction also uses mitosis
What is Meiosis?
produces gametes with one copy of each chromosome the gametes have 23 chromosomes each (humans)
meiosis halves the number of chromosomes before dividing and multiplying , it involves 2 divisions
What does meiosis lead to?
the new cell will be a mixture of the two sets of chromosomes, this is how sexual reproduction produces genetic variation
Define: dominant
an allele that is expressed even when in the presence of a recessive allele –> C
Define: recessive
an allele that is only expressed when present with another recessive allele –> c
What is the scientific name for: Aa
Heterozygous
What is the scientific name for: AA
Homozygous
Define: genotype
this describes the genetic makeup of an individual regarding a particular characteristic
Define: phenotype
this describes the physical appearance of an individual regarding a particular characteristic eg. dimples / no dimples
Advantages of genetic screening
- can check for genetic diseases
- prepare emotionally + financially
- select ‘healthy’ embryos (IVF)
- prepare for early medical intervention
- option of termination
- could save money in long term
Disadvantages of genetic screening
- chance of miscarriage
- should not prevent a life from existing
- select features for ‘designer babies’
- could increase number of terminations
What are stem cells?
unspecialised cells that can differentiate-can change into any type of cell
found in early human embryos and adult bone marrow
can be used to replace faulty cells
Reasons against stem cell research
- human embryos shouldn’t be used since each is a potential life
- uncertainty, may not effectively sure all diseases
- can make arteries narrower, negative impact
- patients bodies might reject them
- morally wrong, if life begins at conception
Reasons supporting stem cell research
- can drastically improve condition of many diseases
- helps to discover cures and treatments
- sickle cell anaemia, bone marrow transplant
- could make heart cells for heart disease or insulin producing cells for those with diabetes
What is therapeutic cloning?
using cells from an adult to produce a cloned early embryo of themselves as a source of perfectly matched embryonic stem cells
could, in theory, be used to heal the original donor
Who was Gregor Mendel and what was his contribution to modern genetics?
the first person to suggest separately inherited factors, which we now call genes
he noted how characteristics were passed on in generations of pea plants
What causes cystic fibrosis and its symptoms?
a recessive allele
organs become clogged with thick, sticky mucus
you can be a carrier
treated by physiotherapy
What is polydactyly?
babies born with extra fingers or toes
dominant allele
What is Huntingdon’s chorea?
rare inherited disease
brain cells degenerate
dominant gene
