Topic 6- Reproduction Flashcards
Reproduction
What are gametes
Sex cells (sperm cells , egg cells,animals)
.Haploid, half the number of chromosomes
What is meiosis
. Form of cell division that reduces the number of chromosomes in the parent cell by half and produces 4 gametes.
what is sexual reproduction
.Involved the production of gametes by mieosis
.a gamete fron each parent formes to create a zygote
.Genetic information from each gamete is mixed so the resulting zygote is unique
What must occur prior to meosis
copies of genetic information are made during this process(the DNA in each chromosome is replicated)
What happens during the first stage of mieosis
. Chromosome number is halved
. The pair of chromosomes are seperated and move to opposite sides of the cell
what happens during the second stage of mieosis
Four unique haploid gametes are produced
Why is mieosis important for sexual reproduction
. It increases genetic variation
.It ensures that the Zygote formed is diploid
Describe fertilisation and its resulting outcome
Gametes join together to restore the normal number of chromosomes and the new cell divides by mitosis
As the embyro develops , cells diffrentiate
What is the advantages of sexual reproduction
. Creates genetic variation in the offsrping
.Increasing the probability of a species adapting and surviving environmental changes.
Disadvantages of sexual reproduction
.More time and energy required,so fewer offspring produced
.Two parents are required
What is a-sexual reproduction
.Produces genetically identical offspring known as daughter cells
.Involved mitosis only
Advantages of a-sexual reproduction
.Lots of offspring can be produced in a short period of time
. Requires less energy , and do not need to mate
Disadvantages of a-sexual reproduction
No genetic variation , except from spontaneus mutations , reducing the probability of a species being able to adapt to environmental change.
Describe the circumstances in which malarial parasites reproduce sexually and a-sexually
.Sexual reproduction in the mosquito
.A-sexual reproduction in the human host
Describe the circumstances in which fungi reproduces sexually and asexually
Asexual reproduction by spores
Sexual reproduction to give variation
Describe the cirumctances in which plants reproduce sexually and asexually
Sexual reproduction to produce seeds
Asexual reproduction by runners
What is DNA
.A double stranded polymer of nucleotides, wound to form a double helix
.The genetic material of the cell found in its nucleus.
Define genome
The entire genetic material of an organism
Why is understanding the human genome important
. Searching for genes linked to different types of disease.
.Understanding and treating inherited disorders
.Tracing human migration patterns from the past
What is a chromosome
. A long coiled molecule of DNA that carries genetic information in the form of genes
How many chromosomes do human body cells have
46 chromosomes 23pairs
Define gene
a small section of DNA that codes fora specific sequence of amino acids which forms a protien.
What are alleles
Different versions of the same gene
What is a dominant allele
A version of a gene where only one is needed for it to be expressed.
What is a recessive allele
A version of a gene where two copies are needed for it to be expressed.
what is meant when an organisnm is Homozygous
When an organism has two copies of the same allele (two recessive or dominant)
What is meant when an organism is heterozygous
When an organism has two different versions of the same gene (one dominant one recessive)
What is the genotype
The genes present for a trait
How are dominant alleles represented in a punnet square
They are represented using uppercase letters
How are recessive alleles represented in a punnet square
They use the lowercase version of the same letter as the dominant allele
Give two examples of inherited disorders
Polydactly- Having extra fingers or toes- Caused by a dominant allele
Cystsic fibrosis- A disorder of cell membranes- caused by a recessive allele
How are embyros screened for inherited disorders
During IVF , one cell is removed and tested for disorder causing alleles.
What are the ethical issues concerning embyro screening
. It could lead to belief in society that having an disorder or disablity , makes on les inferior.
.Many see this as murder, as these unborn babies are humans
.parents put their unreliable reasons first , other than babies wellbeing.
What are the social issues concercning embryo screening
. Social care for children with inherited disorders may need to be considered if parents are unable to provide care
.If an embyro , is found to have an inherited disorder and is terminated , this can prevent a childs from suffering in future.
what are sex chromosomes
.Males have an X and Y chromosome
Females have two X chromosomes
