2.7 Flashcards
What is genetic material called?
DNA
What structure has DNA got?
Double helix
What is found on the DNA?
Genes.
What is a gene? What does it control?
Small section of DNA
Controls your features
What does a gene do ?
Encodes the amino acids in protein
What is chromosome?
Short section of DNA
What do chromosomes contain?
Genes
How many pairs of chromosomes do human cells have?
23
How many copies of each gene do we have ?
2
What is an allele?
Different versions of the same gene
Where are chromosomes found in the human cells?
Nucleus
What happens during the first stage of mitosis?
Cells are copied
What happens in the second stage of mitosis?
Cells are split into 2 identical cells
When does mitosis happen?
During growth
Repairing cells
Asexual reproduction
What are gametes? Where are they found?
Sex cells
Sperm cells (testes) Egg cell (ovaries)
How many chromosomes are in gametes?
23 single chromosomes
What is the first step of meiosis?
Chromosomes are copied
What happens in the second stage of meiosis?
The cell splits into two
What happens in the third stage of meiosis?
The split cells split again
How many cells are produced during meiosis?
4
How many cells are produced in mitosis?
2
What are the newly formed cells made by mitosis like, in terms of their parents?
Genetically identical
Describe the prices of mitosis.
Parent cell Chromosomes make identical copies Line up song centre Spindle fibres separate them Two daughter cells form - identical
What are the stages of meiosis?
Parent cell Chromosomes copy Similar chromosomes pair up DNA gets swapped Chromosomes divide Chromosomes divide again
What is the process of fertilisation?
Fusion of male and female gametes
New cell divides constantly by mitosis
Creates many cells
Creates baby
How are gametes made?
Meiosis
What is a stem cell?
Cells that can change into any type of cell
Stem cells are undifferentiated but can differentiate into any specialised cell
Where can we find stem cells?
Embryos
Bone marrow
What does differentiation mean?
Cells specialise
What can stem cells be used to treat?
Disease such as paralysis
What are the ethical issues of stem cells?
Embryonic- killing human embryo
Why does asexual production lead to offspring having same alleles as its parent?
Same/ identical cells as only one parent
How are your chromosome pairs made up? Of what?
1 from mother
1 from father
How many copies of each gene do we have ?
2
How are dominant alleles shown?
Capital letter
How are recessive alleles shown?
Lowercase letter
What’s the difference between dominant and recessive alleles?
Dominant control features when there is one allele
Recessive controls if they are both recessive alleles
What does genotype mean?
The alleles present
What is meant by phenotype?
The features that alleles produce
What does homozygous mean?
Both alleles are the same
What does heterozygous mean?
Alleles are different
How does DNA fingerprinting identify people?
Everyone’s DNA is different (unique)
How do people get genetic disorders?
Inherited from parents
How are genetic disorders caused?
Faulty alleles
What is meant genetic disorders being carried?
Recessive alleles carry the disorder
What is polydactyly? How is it caused?
Inherited extra fingers or toes caused by dominant alleles
Why can polydactyly not be carried?
It’s a dominant allele
What does cystic fibrosis (CF) cause?
Defective cell membrane
Lung damage
How is CF caused?
Recessive allele -carried
How are some people the carrier of CF but don’t have the disorder?
If the parents each have a heterozygous allele pair then The child will only be a carrier cause they don’t have 2 recessive alleles
How is embryo screening (or PIGD) carried out?
Sperm and egg mixed -fertilised
Fertilised egg develop into embryo (8 cells)
One cell is removed and analysed for CF allele
Health embryo planted into uterus
What is an alternative to embryo screening?
Placenta taken from pregnant woman
If defective allele found it is aborted
What are the pros of embryo screening ?
No abortion needed
Less miscarriage
What are the cons of embryo screening?
Expensive
Healthy left over embryos destroyed
Against religious belief
