Lecture 1: Evolution & Genes Flashcards
‘out of Africa’ hypothesis
about 50,000 years ago homo sapiens started to migrate out of Africa
y-chromosomal adam and mitochondrial eve
the most recent ancestors from which present-day humanity arose
natural selection (darwin)
implies that characteristics may occur more often as a result of a selection procedure consisting of four principles:
- variation
- inheritance
- survival (struggle for existence)
- reproduction rates
pro-creationism
the religiously inspired idea of earth being created by supernatural acts of divine creation (darwin’s ideas go against this)
survival of the fittest
organisms that are not ideally equipped to interact with their environment have a poorer ‘fit’, this limits their chance to survive and reproduce
natural selection
there is no specific plan, the environment plays an important role and evolution is a relatively slow process
selective breeding
a specific, intentional act that produces offspring with particular characteristics that were present in the parental generation
genetic modification
even faster form of selection, where the DNA of an organism is altered. in this way, plants can be made resistant to certain types of toxins so that there is a better chance of harvesting
biogeography
organisms adapt to their specific environments. for example, finches on the Galapagos Islands evolved larger beaks during a drought. this allowed them to survive on the large seeds available
fossil records
sedimentary rock formations allow us to map the time course of evolution. by comparing fossils of skulls to the skulls of their contemporary descendants in their shape and size, it is possible to trace and figure out how and when the organisms evolved
structural similarity
arms, legs, and wings of different species have very similar skeletal structures, which could lead to the conclusion that those species have a shared ancestor
embryology
the different stages an embryo goes through during pregnancy are very similar between different species.
ontogeny recapitulates phylogeny (ernst haeckel)
the essence of the ORP theory is that during embryonic development, every organism goes through all stages of its evolutionary past (embryonic parallelism). human embryo, like fish embryo, go through a stage where they possess gills
molecular biology
modern genetics’ reveals that all organism share common genetic material, supporting the idea of evolution
evolutionary psychology
a branch of psychology that explains behaviors in terms of previous adaptive behaviors in early humans and animals
qualitative traits
often influenced by a single gene and follow a simple pattern of inheritance (such as mendelian inheritance; patterns of inheritance proposed by gregor mendel in which genetic trait is passed from parent to offspring, either dominant/recessive). without the presence of the gene, a person will not posses the trait (all or nothing). usually not affected by environment
quantitative traits
influenced by multiple genes that have only modest contributions, this revolves around the quantity of the presence of certain traits
penetrance
a statistical concept that represents how often the aberrant phenotype (disease/condition) is observed in individuals with the aberrant genotype
allele
one alternative form of a gene, on different chromosomes at the same locus/location
mosaicism
occurs when a person has two or more genetically different sets of cells in their body. if the abnormal cells begin to outweigh the normal calls, it can lead to disease
turner’s syndrome
unusual cell division during early development
polygenetic disorders
enormously complex, this is a disorder with multiple genetic contributions
quantitative trait loci (QTL)
describes how multiple genes at different locations on the chromosomes contribute to the quantitative trait
linkage analysis
geneticists can examine QTLs to look for common events in individuals who have a particular trait or disorder
conspecifics
members of the same species
dichotomous traits
traits that can take on one of two types of traits
phenotype vs genotype
what is observed is called the phenotype and what is genetically transmitted is the genotype
homozygous
each successive generation inherits two alleles/gene variants: one from mother and one from father. if both alleles code for the same trait, they are referred to as homozygous
nucleotide bases
Adenine and Thymine
Cytosine and Guanine
genome
contains all the genetic information of an organism
karyotype (karyogram)
the complete set of chromosomes can be seen as a karyotype often illustrated with a karyogram: all chromosomes in a row. human beings have 46 chromosomes (23 pairs) per cell.
chromatids
during cell division, each chromosome doubles and then temporarily consists of two identical chromatids
centromere
chromatids are attached to the centromere which contains no genetic information
telomeres
repeated genetic sequences at the end of the arms that come off the centromere and the protective reason at the end of a chromosome that safeguards DNA during cell division
cytogenetic bands (loci/gene location)
the stripes seen on chromosomes when examined in detail
male vs female (chromosome)
XY: male
XX: female
chromosomes of humans
a human being has 22 identical pairs (autosomes) from their parents and a set of sex chromosomes
down syndrome
when there are 3 chromosomes on chromosome 21 (21 trisomy)
chromosome
each chromosome is made up of DNA tightly coiled many times around proteins called histones
autosomal dominant example
the root cause of the development of Huntington’s disease is the inheritance of the dominant Huntington’s disease gene
phenylketonuria (PKU)
a form of delayed cognitive development and PKU is caused by a recessive allele. PKU patients lack the enzyme phenylalanine hydrolase which is essential for breaking down the amino acid phenylalanine.
enzyme
is a protein that speeds up chemical reaction inside and outside of cells without itself being used
x-linked recessive hereditary
in some cases, mutations that occur on the x chromosome. the father cannot carry this mutation. in a heterozygous mother, the mutation can be transmitted. when the mother passes the mutated chromosomes onto a daughter and a son, the daughter will be a carrier of the mutation. the son has only one X chromosome, so the recessive mutation will appear in him
functions of deoxyribonucleic acid (DNA)
- genetic information is replicated to make new cells
- DNA has the recipe for protein and determines the function of a cell
each chromosome has (at cell division) two strands of DNA, also referred to as double helix
DNA consists of
carbon, glucose, a nitrogenous base and a phosphate group
characters of the nitrogenous base
adenine (A). cytosine (C), guanine (G), thymine (T). these characters are linked up as A-T and C-G, which are called nucleotides.
codon
three nucleotide bases which determines the code of an amino acid
transcription
the process of reading the DNA code
mRNA (messenger RNA)
during transcription, a strand of DNA behaves as a model for creating mRNA
sickle cell disease
blood disorder characterized by abnormal haemoglobin which occurs when the mRNA carries the wrong information because of an error in the process
exons (transcription)
refer to the base chains that code for protein and are allowed to leave the cell nucleus
introns (transcription)
are noncoding chains
ribosome (protein factories)
the translators of the chain of nucleotide base in the mRNA. ribosome add amino acids when needed, which takes place with the help of tRNA (transfer-RNA)
tRNA
adds the amino acids while ribosomes read the codons. a stop codon causes tRNA and mRNA to stop adding amino acids. this is when the DNA chain is fully transformed into a chain or amino acids that form a protein
function of proteins
- serving as a fuel for energy and heat
- providing the shape and structure of a cell
- serving as receptors in the cell membrane for neurotransmitters or hormones
- forming ribosomes to produce proteins themselves
- forming enzymes to create chemical reactions
- enabling muscle contractions in muscle tissue (actin and myosin)
- carrying oxygen in the blood by joining other proteins and iron
serotonin
there is no gene for serotonin in the body, but there is a gene for the enzymes that produce the neurotransmitter. serotonin is converted from the amino acid L-tryptophan. two enzymes can produce serotonin, other enzymes can inactivate it. DNA control of transcription (epigenetics) can produce more or fewer enzymes for serotonin production and this regulate serotonin levels
polymorphism (type of variation in genes)
differences in DNA sequences among individuals that are present, with a frequency of more than one percent of the population. they have a weak effect or sometimes no effect.
large polymorphisms
large polymorphisms contains a long stretch of DNA called single nucleotide polymorphisms (SNPs)
SNP as a form of mutation
SNP is a form of mutation, but not all mutations are SNPs. we speak of an SNP when the change in DNA has a frequency of more than one percent of the population. The change in DNA can increase the risk of a disorder but it is not a direct cause of a disorder. in addition, there is no genetic patterns to SNPs.
polymerase chain reaction (PCR)
to find SNPs, DNA is amplified with PCR where a known sequence is copied multiple times. when it is copied in sufficient amounts for it to be visualized, a process called electrophoresis is used. in this process, DNA travels through agarose gel block containing microscopic pores.
tandem repeat
a repeated duplication of a DNA chain consisting of short, repeated base pairs. e.g. GATAGATA
chromosomes mutations
deletions can occur during cell division, which is mainly observed during meiosis. This is where a piece of a chromosome breaks off, resulting in chromosome that does not contain the full complement of DNA.
inversions
segments of the chromosome are rotated 180 degrees around: it is the same gene but in the opposite direction. unlike insertions inversion do not change the total amount of genetic material, so inversions do not show phenotypic abnormalities
william-beuren syndrome
result of a the deletion on chromosome 7.
insertions
occur where one or more nucleotides are added
translocations
refer to the movement of a chromosome segment from one chromosome to a non-homogenous chromosome.
types of translocations
- balanced: equal parts of the two chromosome are changed
- unbalanced: involved unequal parts of chromosomes and leads to extra or missing gene
crossing over
refers to two chromosomes directly exchanging genes (parts of their chromosome resulting in non-identical chromatids)
monosomy
when there is only one particular type of chromosomes; an example of this is turner’s syndrome
trisomy
when there are three chromosomes, meaning one is extra
trisomy 21 or down syndrome
when there is an extra chromatid of chromosome 21
polyploidy
having more than two sets of chromosomes, which can be observed in triploidy. this is fatal and results in miscarriage or early death, as fetus is not viable
family studies
the idea that there is a genetic basis for behavior comes from family studies of behavioral genetics. these show the heritable nature of behavioral traits; behaviors that are performed in families. family studies are not concerned with a specific gene; they are more concerned with patterns of inheritance
heredity
a statistical estimate or probability of the contribution of genetic differences to phenotypic differences in traits between people. it is also a proportion of the entire variation that can be explained by genetics and varies between 0 and 1
heritability 0-1
1: would mean that all variation is entirely attributable to genetics
0: would mean that all variation is caused by environmental factors
monozygotic twins (MZ)
genetically identical: they share 100% of their genes
dizygotic twins (DZ)
share as much identical DNA as normal sibling: they share 50% of their genes
shared enviromental influences
characteristics within an environment or a family that all members share, whether they are MZ or DZ twins or ordinary siblings
non-shared influences
refers to the environmental influences that are unique to the individuals within the family. the non-shared environmental also refers to MZ, DZ, and common sibling
endophenotype
when information about the genes and environment in a person with a particular disorder needs to be supplemented
turkheimer (2000)
suggested that there are three laws of behavioral genetics:
- all human behavior traits are hereditary
- the effect of upbringing in the same family has a smaller effect compared to the effect of genes
- a substantial portion of the variation in complex human behavioral traits is not accounted for by the effects of genes or families
adoption studies
work with the idea that siblings of the same parents given up for adoption share the same genes, but not environment with their biological parents
adoption studies 2
allows the similarities between the child and the biological parent to be attributed to genes. conversely, the children in a family with adopted children share the environment with their adoptive parents, and not their genetics. if the child shows similarities to their adoptive parents, it is attributable to environmental factors
candidate gene
a gene located in a chromosomal region that may be involved in a genetic disorder
depression
- there is no depression gene
- 50/50 genetics/other physical or psychological factors
- depression appears to result from combinations of genetic changes that increase susceptibility
