Week 2 Flashcards
Beginnings (42 cards)
The nucleus of each human cell (with the exception of sex cells) contains how many chromosomes?
23 pairs (46 total, one chromosome in each pair from the mother, one from the father)
Chromosomes are composed of complex molecules known as…
Dna (Deoxyribonucleic Acid)
DNA in the chromosomes is organised into segments called…
Genes
What is a key distinction between male and female genomes?
In a male structure, the 23rd pair is ‘XY’, rather than ‘XX’
Genotype…
The totality of an individual’s genes
Phenotype…
Refers to the actual characteristics of an individual. What is seen or observed, e.g. height, weight, intelligence, personality
Dominant genes..
Refer to the expressed characteristics
Recessive genes…
are not expressed. although part of the genotype
Dominant-recessive inheritance…
a pattern in which a pair of chromosomes contains one dominant and one recessive gene, but only the dominant gene is expressed in the phenotype, e.g. blood type, eye colour
Allele
Alternative form of a gene. On a pair of chromosomes, each of two forms a gene
Incomplete Dominance…
In which the phenotype influenced primarily but not exclusively by the dominant gene
e.g. sickle cell trait
Polygenic Inheritance
Refers to the expression of phenotypic characteristics due to interaction of multiple genes, e.g. skin colour
Why are males more susceptible than females to developing various recessive disorders, such as haemophilia and colour blindness?
‘X-linked inheritance’
Having only one X chromosome makes males more vulnerable. the reason for this is that if a female has one X chromosome that contains the recessive gene for a disorder, the disorder will not show up in her phenotype because the dominant gene on her other X chromosome will prevent it from being expressed. She will be a carrier of the disorder to the next generation but will not have the disorder herself.
Heritability
An estimate of the extent to which genes are responsible for differences among persons with a specific population
Concordance rates…
Percentage that indicates degree of similarity in phenotype among pairs of family members
Epigenesis..
the continuous bidirectional interaction between genes and the environment, e.g. in agouti mice, a diet rich in methyl donors during pregnancy can modify DNA methylation, leading to darker coat colours in offspring by silencing the agouti gene, demonstrating epigenetic inheritance.
Three different kinds of genotype?
Passive- occur in biological families because parents provide both genes and environment for their children.
Evocative- occur when a person’s inherited characteristics evoke responses from others in their environment.
Active- occur when people seek out environments that correspond to their genotypic characteristics, a process called niche picking.
Teratogens…
behaviours, environments, and bodily conditions that could be harmful
In what period is foetus most vulnerable to teratogens?
Embryonic (3-8 weeks)
What are the odds of a woman giving birth to a child with Down Syndrome after the age of 45?
1 in 30
Genetic mutation…
a permanent alteration of a DNA sequence that makes up a gene.
As a man gets older, his sperm contains more mutations; that is, more genetic mistakes are made in the production of sperm during meiosis. These mutations contribute to problems in the course of development.
Types of prenatal diagnostic tests…
-Ultrasound
-Foetal MRI
-Chorionic Villus Sampling (CVS)
-Amniocentesis
-Maternal blood screening
-Non-invasive pre-natal diagnosis (NIPD)
Ultrasound…
high-frequency sound waves are directed towards the uterus, and as they bounce off the fetus they are converted by computer into an image that can be viewed on a screen.
Amniocentesis…
a long hollow needle is inserted into the pregnant woman’s abdomen and, using the ultrasound image for guidance, a sample of the amniotic fluid is withdrawn from the placenta surrounding the fetus.
The cells can be examined for information on the fetus’s genotype.
Amniocentesis is conducted 15–20 weeks into pregnancy. It is used only for women who are at risk for prenatal problems because it carries a small risk of triggering miscarriage. It can detect 40 different defects in fetal development with 100% accuracy
