B1 - You and Your Genes Flashcards
What are genes?
instructions to control how an organism develops and functions are found in the nucleus of its cells. Describe how to make proteins
What are examples of structural and functional proteins?
Structural- collagen
Functional- amylase
What are characteristics determined by?
Genetics (eye colour) Many genes work together to form eye colour
Environment (scars)
combination (weight)
chromosomes in a pair carry the same genes in the ________ place, but that
there may be _______ versions of genes called alleles
same
different
How many alleles does an individual usually have for a gene?
2
What is heterozygous?
When the two alleles of a gene are different
What is homozygous?
When the two alleles of a gene are the same
Why do siblings have similarities?
because of the combination of
maternal and paternal alleles in the fertilised egg.
Why do siblings have differences?
different offspring from the same parents can differ from each other because
they inherit a different combination of maternal and paternal alleles
an individual with one or both dominant alleles (in a pair of alleles) _______ show the
associated dominant characteristic
will
an individual with one recessive allele (in a pair of alleles) ____________ show the associated
recessive characteristic
will not
an individual with both recessive alleles (in a pair of alleles) _________ show the associated
recessive characteristic
will
What sex chromosomes do human males have?
XY
What sex chromosomes do human females have?
XX
How is sex determined?
the sex-determining gene on the Y chromosome triggers the development of testes, and that in the absence of a Y chromosome ovaries develop
What is genotype?
the genetic make-up of an organism
the combination of alleles
What is phenotype?
the observable characteristics that the organism has.
How are genetic disorders caused?
Faulty alleles of a single gene
What is an example of a genetic disorder caused by dominant alleles?
Huntington’s disease
What is an example of a genetic disorder caused by recessive alleles?
Cystic fibrosis
What are the symptoms of huntington’s?
– late onset, tremor, clumsiness, memory loss, inability to
concentrate, mood changes
What are the symptoms of cystic fibrosis?
thick mucus, difficulty breathing, chest infections, difficulty in digesting food
What is a carrier?
a person with one recessive allele (in a pair of alleles) will not show the symptoms of the disorder, but can pass the recessive allele to their children
What is pre-implantation genetic diagnosis?
Pre-implantation genetic diagnosis (PGD) is a procedure used on embryos before implantation. Fertility drugs are taken by the female so that several eggs are released and collected by a doctor. These eggs are then fertilised in a Petri dish by sperm, either from the father or a donor. (IVF) Once the embryos have reached the eight-cell stage, one cell is removed from each.
The cells are tested for the allele posing a risk (for example the Huntington’s allele). This is known as PGD. Embryos that don’t contain the unwanted allele are then implanted into the uterus to hopefully create a lower risk, full-term pregnancy.
What is predicted testing?
This is used to detect genetic disorders where the symptoms develop later in life, such as Huntington’s disorder. Predictive testing can be valuable to people who have no symptoms but have a family member with a genetic disorder. The results can help to inform decisions about possible medical care.
Testing an individual before prescribing drugs
?
What are implications that need to be considered in the genetic testing of adults and embryos?
a. risk of miscarriage as a result of cell sampling for the genetic test
b. using results that may not be accurate, including false positives and false negatives
c. whether or not to have children at all
d. whether or not a pregnancy should be terminated
e. whether other members of the family should be informed
What are implications for testing embryos for embryo selection prior to implantation?
Some believe life begins at conception - destruction of an embryo=destruction of a person
While PGD helps reduce the chances of conceiving a child with a genetic disorder, it cannot completely eliminate this risk. In some cases, further testing is needed during pregnancy to ascertain if a genetic factor is still possible.
Although genetically present, some diseases only generate symptoms when carriers reach middle age. The probability of disorder development should be a topic of discussion with the healthcare provider.
What are the implications of the use of genetic testing by others (such as employers and insurers)
People may feel discriminated against?
How do clones occur naturally? (not animals)
bacteria, plants and some animals can reproduce asexually to form clones
Why are there sometimes differences between clones?
any differences between clones are likely to be due only to environmental factors
When do clones occur naturally in plants?
clones of plants occur naturally when plants produce bulbs or runners
When do clones of animals occur?
a. naturally, when cells of an embryo separate (identical twins)
b. artificially, when the nucleus from an adult body cell is transferred to an empty
unfertilised egg cell
What are the different types of stem cells?
a. adult stem cells which are unspecialised cells that can develop into many, but not all,
types of cells
b. embryonic stem cells which are unspecialised cells that can develop into any type of cell
What are the benefits of stem cells being unspecialised?
offer the potential to treat some illnesses
When do the majority of cells in multicellular organisms become specialised?
during the
early development of the organism.
