Reproduction Flashcards
1
Q
What does the acrosome reaction do on sperm cells?
A
- the acrosome in the head of the sperm swells, fuses with the sperm cell surface membrane and release digestive enzymes
- these breakdown the zona pellucida of the ovum
- this is called the acrosome reaction
2
Q
What are gametes? What are the gametes in mammals and plants? What do gametes fuse together to form?
A
- gametes are sex cells
- the sperm and egg in mammals
- in plants the sex cells are pollen in male and ovules in female
- gametes fuse during fertilisation to form zygotes
3
Q
What does haploid refer to?
A
- haploid refers to the presence of a single set of chromosomes in an organisms cells
4
Q
What are the two different types of cell division?
A
- mitosis and meiosis
5
Q
How do gametes form?
A
- mitosis = produces new as an organism grows and develops. This retains the full number of chromosomes known as the diploid number (2n) (46 in humans)
- meiosis = produces gametes with only half the number of chromosomes, called the haploid number (n) (23 in humans)
6
Q
What is a zygote?
A
- a zygote is the cell formed when two gametes fuse during fertilisation
7
Q
What is the zona pellucida?
A
- (the zona pellucida surrounds the ovum and is a jelly-like coating)
8
Q
What is an oocyte?
A
- the oocyte is an immature female sex cell
- an immature egg has not undergone the necessary cell division to reduce the number of chromosomes in the nucleus of the egg from 46 chromosomes to 23 chromosomes
9
Q
What are follicle cells?
A
- follicle cells are cells that surround the oocyte within the follicle
10
Q
What is the cortical reaction?
A
- once a sperm fuses with and penetrates the membrane surrounding the egg, chemicals released by the ovum cause the zona pellucida, to thicken, preventing any further sperm entering the egg
- this process is called the cortical reaction
11
Q
How are egg cells adapted for its function?
A
- they are larger than sperm cells as they contain food stores (to nourish growing embryo)
- have follicle cells that form a protective coating
- have a jelly-like glycoprotein layer, known as the zona pellucida, that forms an impenetrable barrier after fertilisation by a sperm cell has occurred, to prevent other sperm nuclei from entering the egg
12
Q
How are sperm cells adapted for their function?
A
- sperm cells have a flagellum that allows them to swim towards the egg cell
- contain many mitochondria that provide energy for movement of the flagellum (swimming)
- an acrosome that contains digestive enzymes to break down/ penetrate the zona pellucida
13
Q
Why is it important for gametes to be haploid?
A
- its important because it ensures that a diploid gamete forms after fertilisation
- it prevents doubling of the chromosome number
14
Q
How much genetic information do gametes contain?
A
- gametes contain only half the genetic information found in normal body cells
- they are haploid (the sperm and egg cells contain 23 single chromosomes in their nucleus)
15
Q
What would happen if gametes were diploid?
A
- if they were diploid, the chromosome number would double between generations, leading to multiple copies of the same chromosomes
- this could have a very negative impact on the growth and development of the organism
