B13: Reproduction Flashcards
Why is there no variation in offspring that are made as a product of asexual reproduction?
There is no fusion of special sex cells (gametes).
How does asexual reproduction work?
Cells divide by mitosis
What are produced as a result of asexual reproduction?
Identical offspring (clones)
In what is asexual reproduction very common?
The smallest animals and plants (plants like daffodils, strawberries and brambles too)
What does sexual reproduction involve?
A male sex cell and a female sex cell fusing together to form a zygote, which develops to form a new individual
How are gametes formed?
Through meiosis
What happens during meiosis?
The chromosome number halves, so there are two sets of each chromosome inherited from the mother and one from the father.
What are the gametes in plants?
Egg cells and pollen
What are the gametes in animals?
Egg cells and sperm
What happens when a cell divides to form gametes?
The genetic info is copied so there are 4 sets of each chromosome. Each chromosome forms a pair of chromatids.
The cell then divides twice to form four gametes, each with a single set of chromosomes.
What are the advantages of asexual reproduction?
-only one parent needed
-faster than sexual reproduction
What are the disadvantages of asexual reproduction?
-If one organism cannot survive, none can.
What are the disadvantages of sexual reproduction?
-two parents needed
-slower than asexual reproduction
What are the advantages of sexual reproduction?
-the variation means if the environment changes, they wont go extinct.
What is the most common form of reproduction in fungi?
Asexual
In what conditions do some fungi reproduce sexually?
In dry conditions
What are some examples of asexual reproduction in plants?
Strawberry plants, spider plants, daffodils
What is DNA?
A long molecule made up of many repeating units
What are genes?
Small sections of DNA
Put the parts of DNA in size order?
DNA > chromosome > gene > sequence of amino acids that make a specific protein
What is a genome?
The entire genetic material of the organism
Why is learning more about the human genome important?
-Helps us understand inherited disorders (cystic fibrosis, sickle cell)
-helps us search for genes linked to different diseases
Helps us pick the best treatment for cancers for each individual
-helps us understand human evolution and history
The long strands of DNA are made up of alternating ——- and ———— sections.
Sugar and phosphate sections.
What 4 letters represent the bases in DNA?
A,C,G & T
What is the combination of a sugar, a phosphate and a base called?
A nucleotide
How many nucleotides are in a group?
3
Each group of - bases codes for a particular ——— ———.
3, amino acids
A change or mutation can ———— or ———- the whole protein structure and the way it works.
Change or disrupt
In what pairs do the base letters couple up with each other?
C&G. T&A
How are proteins made from DNA?
- Genes in the DNA produce a template for the protein. It reflects the sequence of bases in DNA.
2.the template leaves the nucleus and binds to the surface of a ribosome. - The cytoplasm contains carrier molecules that are attached to an amino acid.
- The CMs attach themselves to the template.
- The amino acids are joined together to form a specific protein.
- CMs keep bringing AAs to add to the protein chains until the template is completed.
- protein detaches from the CMs and the CMs detach from the template and go back to cytoplasm to get more AAs.
When is a gene said to be expressed?
When a gene codes for a protein that is synthesised in the cell
What is one thing that scientists have discovered that the non-coding parts of DNA do?
Switching genes on and off.
What are mutations?
Changes in existing genes
What can happen as a result of mutations?
-the active site changing shape and an enzyme losing its strength
- the active site changing shape and an enzyme becoming stronger
What does homozygote mean?
An individual with two identical alleles for a characteristic (e.g. BB or bb)
What does heterozygote mean?
An individual with different alleles for a characteristic (e.g. Bb)
What does genotype mean?
It describes the alleles present or genetic makeup of an individual regarding a particular characteristic (e.g. Bb, bb)
What does phenotype mean?
It describes the physical appearance of an individual regarding a particular characteristic (e.g. black or brown fur in a mouse)
What are the sex chromosomes in females and males?
Female= XX
Male= XY
Every pregnancy has a —/— chance of it being a boy, or girl.
50/50 chance
What occurs when you have polydactyly?
You get extra fingers and/or toes.
Is polydactyly caused by a dominant or recessive allele?
Dominant
What does cystic fibrosis cause?
It causes your cell membranes to prevent the movement of certain substances and means the mucus made in areas of the body becomes very thick.
Your lungs stop working properly because they get clogged up.
The pancreas can’t secrete enzymes properly because they’re clogged.
You become infertile.
How does cystic fibrosis affect the body?
It affects many organs of the body, especially the lungs, the digestive system and the reproductive system.
How is cystic fibrosis treated?
Physiotherapy and antibiotics to keep the lungs clear of mucus. Enzymes replace the ones the pancreas can’t produce.
THERE IS NO CURE!
Is cystic fibrosis caused by a recessive or dominant allele?
Recessive
What makes someone a carrier of cystic fibrosis?
They have the allele but don’t suffer from the condition.
Is there currently a way to cure genetic disorders?
Nope
When is aminocentesis carried out?
At around 15-16 weeks of pregnancy
What does aminocentesis involve?
Taking some of the fluids from around the fetus, it contains fetal cells which can be used for genetic screening
When does chorionic villus happen?
Between 10-12 weeks of pregnancy
What does chorionic villus involve?
Taking a small sample of tissue from the developing placenta, to provide fetal cells to screen
What risks are there from chorionic villus and aminocentesis?
Miscarriage
What happens during genetic screening after you have the cells?
The DNA is isolated from the embryo cells and tested for specific disorders.
What are problems with embryo screening?
- risk of miscarriage
-false positives and negatives
-expensive
