Development and inheritance

Question 1

Why is cell differentiation important?

Answer 1

It enables the formation of specialized tissues with specific functions like muscle tissue

Question 2

What are embryonic stem cells?

Answer 2

Stem cells found in very early embryos that are unspecialized and capable of differentiating into any cell type.

Question 3

What is the function of embryonic stem cells?

Answer 3

Enable the growth and development of tissues in human embryos

Question 4

Where can embryonic stem cells be collected from?

Answer 4

Donor stem cells removed from embryos grown in vitro or patient’s own stem cells removed from the umbilical blood before birth

Question 5

What are adult stem cells?

Answer 5

Stem cells that can differentiate into a limited range of cell types. For example bone marrow stem cells

Question 6

Describe the potential uses of stem cells in medicine

Answer 6

-treating diseases like heart disease and type 1 diabetes
-to repair damaged tissue
-scientific research
-growing organs for transplants

Question 7

What are the ethical issues related to the use of stem cells in medicine?

Answer 7

-the embryos to provide the stem cells are destroyed, which is seen as unethical and waste of potential human life
-could lead to the ‘farming’ of embryos for stem cells
-may lead to the reproductive cloning of humans

Question 8

What is a pluripotent stem cell?

Answer 8

A type of stem cell which can differentiate into any type of cell in the body.

Question 9

What is a totipotent stem cell?

Answer 9

A type of stem cell which can differentiate into any type of cell in the body or into cells which make up extra-embryonic tissues like the placenta

Question 10

What is a morula?

Answer 10

A cluster of 16 cells formed from divisions of the zygote

Question 11

What is the blastocyst?

Answer 11

A structure formed from further division and cleavage of the morula around 5 days after fertilization. It has an outer layer, fluid cavity and an inner cell mass.

Question 12

What is gene expression?

Answer 12

The synthesis of active functional products through the transcription and translation of a gene

Question 13

What is pre-mRNA?

Answer 13

The direct product of transcription before splicing occurs

Question 14

How is pre-mRNA converted to mature mRNA?

Answer 14

Post-transcriptional modifications and splicing alter the structure of the mRNA molecule to remove introns

Question 15

What is mature mRNA?

Answer 15

The product of splicing which includes only exons. This is then used in translation to produce functional polypeptides

Question 16

How can one gene give rise to multiple polypeptides?

Answer 16

Through alternative splicing where different exons are joined together in different orders to produce different mRNA molecules.

Question 17

Define genotype

Answer 17

The genetic constitution of an organism

Question 18

Define phenotype

Answer 18

The expression of an organism’s genetic constitution, combined with its interaction with the environment.

Question 19

What are epigenetic modifications?

Answer 19

Modifications which cause changes in gene expression that are not due to alterations in the nucleotide base sequence of DNA

Question 20

What are histones?

Answer 20

Proteins which help to package DNA tightly in the form of chromatin. The DNA coils around the histone proteins

Question 21

Name two types of epigenetic modifications

Answer 21

DNA methylation and
Histone acetylation

Question 22

What is DNA methylation?

Answer 22

Addition of methyl groups to cytosine bases in DNA. It typically down regulates transcription

Question 23

What is Histone acetylation?

Answer 23

Addition of acetyl groups to histone proteins which make them bind less tightly to DNA molecules and allow for increased transcription

Question 24

Describe briefly what happens to epigenetic modifications after cell division

Answer 24

Many epigenetic modifications are lost during cell division. Some specific ones are retained during production of new histones, Each new DNA strand gets a mix of old and new histones, so some modifications are retained.

Question 25

What is polygenic inheritance?

Answer 25

The control of a trait by multiple genes

Question 26

What is multiple allele inheritance?

Answer 26

How multiple different versions of the same gene affect a trate

Question 27

What type of variation does polygenic inheritance give rise to?

Answer 27

Continuous variation

Question 28

What is continuous variation?

Answer 28

Variation that cannot be categorized. It produces a continuous range (e.g. height and weight)

Question 29

What is discontinuous variation?

Answer 29

Variation that can be categorized into distinct groups like eye color or blood group.