TOPIC 3 Flashcards

Question

Describe the cortical reaction.

Answer 1

1) The sperm nucleus enters the ovum 2) Enzymes released from lysosomes in the ovum thickens the jelly like layer, preventing entry from other sperm 3) Nucleus of both gametes fuse to produce zygote

Answer 2

1) Chromosomes replicate before division- they are made up of two strands of genetic material, two chromatids 2) Meiosis 1- Homologous chromosomes pair up and separate 3) Chromatids separate and gametes are formed, each with half of the original chromosomes.

Answer 3

Independent assortment is a principle in meiosis that states that during the formation of gametes, the distribution of alleles for different traits is random and independent of one another. This means that the segregation of one pair of alleles (from one parent) during meiosis is independent of the segregation of another pair of alleles (from the other parent), resulting in a variety of possible combinations of traits in offspring.

Answer 4

During meiosis 1, homologous chromosomes come together as pairs and all four chromatids come into contact. At these points, the chromatids break and rejoin, exchanging sections of DNA between non-sister chromatids. These points are chiasmata and there are several along the lengths of each pair of chromosomes, giving rise to a large amount of variation.

Answer 5

There isn't.

Answer 6

G1, S1, G2

Answer 7

the chromosomes shorten and thicken (condense) to be visible as two identical replicated chromatids (strands). They are joined at the centromere. Then, the spindle forms- and the centrioles move around the nuclear envelope and position themselves at opposite poles of the cell, followed by the spindle fibres forming between the poles. The nuclear envelope then breaks down.

Answer 8

the chromosomes’ centromeres attach to the spindle fibres at the equator (widest part of the spindle).

Answer 9

the centromeres split and the spindle fibres shorten and pull the halves of the centromere in each direction, toward the poles of the cell. The spindle proceeds to break down.

Answer 10

the chromosomes unravel and the nuclear envelope reforms such that the two sets of genetic information are enclosed in separate nuclei.

Answer 11

the new cell surface membranes constricts around the centre of the cell.

Answer 12

G1 the cell grows in size, and performs its normal metabolic functions, such as protein synthesis and energy production. G1 phase is also a period of intense biochemical activity in which the cell prepares itself for DNA replication, which occurs during the next phase, S phase. S1 During the S phase (Synthesis phase), the cell replicates its DNA in preparation for cell division. G2 Synthesis of organelles Protein synthesis The centrosomes replicate and the spindle fibres assemble

Answer 13

Totipotent stem cell

Answer 14

A stem cell which can give rise to many different specialised cells, but not to an entire organism

Answer 15

Only certain types of cells, not an entire organism

Answer 16

Stem cell = undifferentiated basic cells that have the potential to give rise into any specialised cell

Answer 17

Multipotency = adult stem cells that have the ability to form a variety of different cell types

Answer 18

Despite the stem cells having the same genome, they are able to specialise into a diverse range of cell types because during differentiation certain genes are expressed ('switched' on)

Answer 19

Under certain conditions, some genes in a stem cell are activated, whilst others are inactivated mRNA is transcribed from active genes only This mRNA is then translated to form proteins These proteins are responsible for modifying the cell (e.g. they help to determine the structure of the cell and the processes that occur within the cell) As these proteins continue to modify the cell, the cell becomes increasingly specialised The process of specialisation is irreversible (once differentiation has occurred, the cell remains in its specialised form)

Answer 20

a protein that controls the transcription of genes by binding to a specific region of DNA, they control gene expression

Answer 21

An operon is a section of DNA that includes: A cluster of structural genes that are transcribed together (these code for useful proteins e.g. enzymes) Control elements, including a promoter region (a DNA sequence that RNA polymerase initially binds to) and an operator region (where transcription factors bind) Some operons may include regulatory genes that code for activators or repressors

Answer 22

The lac operon controls the production of the enzyme lactase (also called β-galactosidase) and two other structural proteins

Answer 23

Lactase breaks down the substrate lactose so that it can be used as an energy source in the bacterial cell

Answer 24

The components of the lac operon are found in the following order: Promoter for structural genes Operator Structural gene lacZ that codes for lactase Structural gene lacY that codes for permease (allows lactose into the cell) Structural gene lacA that codes for transacetylase Located to the left (upstream) of the lac operon on the bacterium's DNA there is also the: Promoter for regulatory gene Regulatory gene lacI that codes for the lac repressor protein

Answer 25

The lac repressor protein has two binding sites that allow it to bind to the operator in the lac operon and also to lactose (the effector molecule)

Answer 26

When it binds to the operator it prevents the transcription of the structural genes as RNA polymerase cannot attach to the promoter When it binds to lactose the shape of the repressor protein distorts and the repressor protein can no longer bind to the operator

Answer 27

The following processes take place when lactose is absent in the medium that the bacterium is growing in: The regulatory gene is transcribed and translated to produce lac repressor protein The lac repressor protein binds to the operator region upstream of lacZ Due to the presence of the repressor protein RNA polymerase is unable to bind to the promoter region Transcription of the structural genes does not take place No lactase enzyme is synthesized

Answer 28

There is an uptake of lactose by the bacterium The lactose binds to the second binding site on the repressor protein, distorting its shape so that the repressor protein cannot bind to the operator region RNA polymerase is then able to bind to the promoter region and transcription takes place The mRNA from all three structural genes is translated The enzyme lactase is produced and lactose can be broken down and used for energy by the bacterium

Answer 29

There is an uptake of lactose by the bacterium The lactose binds to the second binding site on the repressor protein, distorting its shape so that the repressor protein cannot bind to the operator region RNA polymerase is then able to bind to the promoter region and transcription takes place The mRNA from all three structural genes is translated The enzyme lactase is produced and lactose can be broken down and used for energy by the bacterium

Answer 30

The more potency it loses

Answer 31

When does an embryo become a human w/ human rights? Is it acceptable to use human embryos specially created for research? Is it acceptable to remove the chance of life from the embryo in fused cells?

Answer 32

the process by which information from a gene is used in the synthesis of a functional gene product

Answer 33

Correct stimulus is given to unspecialised cells Some genes are switched on and become active, others switched off mRNA is made from the active genes only mRNA goes to the ribosome to be read and protein is made The protein can permanently alter the structure and function of the cells

Answer 34

the study of changes in organisms caused by modification of gene expression

Answer 35

Separate each section and see what grows, and what it grows into The stem didn’t grow and the tip only grew a matching hat not a rhizoid Cut the hat off, then the rhizoid later on and see what hat grows A matching hat grew but the rhizoid did not grow back Cut the rhizoid and hat off, and move the nucleus to the stem and see if/what grows The matching hat and rhizoid grew back Swap the stem and cut the hat off, and see what hat grows, then cut the hat off again The first hat was an intermediate hat The second hat matched the rhizoid Shows that DNA is left in the stem, the rhizoid with the nucleus controls the growth of everything, the tip can only regrow a stem and hat from the DNA left in the tip

Answer 36

a mixture of chemical markers that ‘instruct’ genes/ are attached to histone proteins It affects the phenotype w/o affecting genotype

Answer 37

A group of specialised cells working together to carry out one function A group of tissues working together to carry out one function A group of organs working together to carry out a particular function

Answer 38

The enzyme in the lac operon model which breaks down lactose. It is transcribed by the DNA in the lac operon and a lac repressor molecule prevents its production.

Answer 39

This stops the RNA polyemerase from binding to the promoter

Answer 40

The binding of epigenetic markers to histone tails alters how tightly DNA winds around histone proteins

Answer 41

Deactivates it, prevents transcription into mRNA

Answer 42

a locus (plural = loci) is the location of genes on a chromosome.

Answer 43

outward expression of a cell or organism due to the interaction of: Genotype: Genetic differences leading to outward differences Environment: Environmental differences leading to outward differences

Answer 44

The genes that control the development of a section of an organisms structure.

Answer 45

1) Data that falls in discrete groups with no overlap 2) Data that falls within any value within certain range.

Answer 46

Oncogenes, Tumour suppressor genes

Answer 47

genes which code for proteins that stimulate the transition from one stage of the cell cycle to the next stage. Mutations/ less methylation can lead to the cell cycle being continuously active.

Answer 48

produce suppressor proteins which stop the cell cycle

Answer 49

Some genes are only present on one sex chromosome and not the other As the inheritance of these genes is dependent on the sex of the individual they are known as sex-linked genes Most often sex-linked genes are found on the longer X chromosome If the gene is on the X chromosome, males (XY) will only have one copy of the gene, whereas females (XX) will have two Because males only have one X chromosome, they are much more likely to show sex-linked recessive conditions (such as red-green colour blindness and haemophilia) Females, having two copies of the X chromosome, are likely to inherit one dominant allele that masks the effect of the recessive allele

Answer 50

As its name implies, autosomal linkage only occurs on the autosomes (any chromosome that isn’t a sex chromosome) Two or more genes on the same autosome do not assort independently during meiosis Instead, these genes are linked and they stay together in the original parental combination These linked genes are passed on to offspring all together (through the gametes)

TOPIC 3 Flashcards

(78 cards)