Development and inheritance Flashcards
Why is cell differentiation important?
It enables the formation of specialized tissues with specific functions like muscle tissue
What are embryonic stem cells?
Stem cells found in very early embryos that are unspecialized and capable of differentiating into any cell type.
What is the function of embryonic stem cells?
Enable the growth and development of tissues in human embryos
Where can embryonic stem cells be collected from?
Donor stem cells removed from embryos grown in vitro or patient’s own stem cells removed from the umbilical blood before birth
What are adult stem cells?
Stem cells that can differentiate into a limited range of cell types. For example bone marrow stem cells
Describe the potential uses of stem cells in medicine
-treating diseases like heart disease and type 1 diabetes
-to repair damaged tissue
-scientific research
-growing organs for transplants
What are the ethical issues related to the use of stem cells in medicine?
-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
What is a pluripotent stem cell?
A type of stem cell which can differentiate into any type of cell in the body.
What is a totipotent stem cell?
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
What is a morula?
A cluster of 16 cells formed from divisions of the zygote
What is the blastocyst?
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.
What is gene expression?
The synthesis of active functional products through the transcription and translation of a gene
What is pre-mRNA?
The direct product of transcription before splicing occurs
How is pre-mRNA converted to mature mRNA?
Post-transcriptional modifications and splicing alter the structure of the mRNA molecule to remove introns
What is mature mRNA?
The product of splicing which includes only exons. This is then used in translation to produce functional polypeptides
How can one gene give rise to multiple polypeptides?
Through alternative splicing where different exons are joined together in different orders to produce different mRNA molecules.
Define genotype
The genetic constitution of an organism
Define phenotype
The expression of an organism’s genetic constitution, combined with its interaction with the environment.
What are epigenetic modifications?
Modifications which cause changes in gene expression that are not due to alterations in the nucleotide base sequence of DNA
What are histones?
Proteins which help to package DNA tightly in the form of chromatin. The DNA coils around the histone proteins
Name two types of epigenetic modifications
DNA methylation and
Histone acetylation
What is DNA methylation?
Addition of methyl groups to cytosine bases in DNA. It typically down regulates transcription
What is Histone acetylation?
Addition of acetyl groups to histone proteins which make them bind less tightly to DNA molecules and allow for increased transcription
Describe briefly what happens to epigenetic modifications after cell division
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.
What is polygenic inheritance?
The control of a trait by multiple genes
What is multiple allele inheritance?
How multiple different versions of the same gene affect a trate
What type of variation does polygenic inheritance give rise to?
Continuous variation
What is continuous variation?
Variation that cannot be categorized. It produces a continuous range (e.g. height and weight)
What is discontinuous variation?
Variation that can be categorized into distinct groups like eye color or blood group.
