Topic 3B : Reproduction & Inheritance Flashcards

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1
Q

How are mammalian eggs adapted for their function ?

A

The mammalian eggs have a zona pellucida which is a protective outer layer which the sperm has to penetrate in order for fertilisation to occurs and it also prevents polyspermy

The mammalian eggs have a haploid nucleus to restore a full set of chromosomes at fertilisation

The mammalian eggs also contain loads of nutrients which are essential for embryo development

The mammalian eggs have cortical granules which release substances which cause the zona pellucida to harden

The mammalian egg also has follicle cells which form a protective coating around the egg

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2
Q

How are mammalian sperm adapted for their function ?

A

The mammalian sperm contain many mitochondria to provide energy for the rotation of the flagellum which enables the cell to move

The mammalian sperm has acrosomes which contain digestive enzymes which break down the zona pellucida and allow the sperm to penetrate the egg

The mammalian sperm also contains a haploid nucleus to restore a full set of chromosomes at fertilisation

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3
Q

Describe the process of mammalian fertilisation

A

The sperm swim towards the egg

Once a sperm makes contact with the zona pellucida of the egg the acrosome reaction occurs where digestive enzymes are released from the acrosome of the sperm and digest the zona pellucida so that the sperm can move through it to the cell membrane of the egg cell

The sperm head fuses with cell membrane of the egg triggering cortical reaction where egg releases cortical granules in vesicles which contain chemicals that cause the zona pellucida to thicken making it impenetrable to other sperm (polyspermy)

Sperm nucleus enters the cell and the tail is discarded

The nucleus of sperm fuses with the nucleus of the egg

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4
Q

Where does fertilsation occur?

A

In the oviduct of the female reproductive system

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5
Q

In mammals, where is sperm deposited?

A

The sperm is deposited high up in the female vagina close to the entrance of the cervix meaning that in order for fertilisation to occur the sperm has to make its way up through the cervix and the uterus to the oviduct

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6
Q

What is the product of fertilisation?

A

Fertilisation between egg and sperm produces a diploid zygote which contains a full set of chromosomes

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7
Q

blastocyst

A

when a zygote becomes a blastocyst after a week of fertilisation/cell division

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8
Q

structure of blastocyst

A

fluid filled cavity forms

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9
Q

state the fate of the cells in a blastocyst

A

outer cells become placenta as they are totipotent

inner pluripotent cells become foetus

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10
Q

meiosis

A

cell division that happens in the reproductive organs and produces genetically different gametes

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11
Q

explain why it is important for gametes to be haploif

A

so when they join, the original diploid chromosome number will be restored

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12
Q

describe the outcome of meiosis and what happens to these cells in male and female organisms

A

four haploid cells and these in males become sperm and in females become eggs

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13
Q

state two ways in which meiosis can produce genetic variation

A

crossing over of chromatids

independent assortment of chromosomes

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14
Q

describe the process of crossing over

A

homologous pairs of chromosomes come together and pair up

two of the chromatids in each homologous pair twist around each other and twisted bits break off their original chromatid snd rejoin onto the other chromatid recombining their genetic material

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15
Q

how does crossing over of chromatids creates genetic variation

A

after they cross over, chromatids contain the dame genes but they now have a different combination of alleles

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16
Q

describe the process of independent assortment

A

the different combinations of chromosomes from your parents and when the gametes produced have different combinations of those maternal and paternal chromosomes go into each cell

17
Q

locus

A

the position of a gene on a chromosome