chapter 2 Flashcards
mechanisms of heredity: autosomes
first 22 pairs of chrosomes (these are all matching pairs)
mechanisms of heredity: sex chromosomes
these are the 23rd pair of chromosomes, these determine the sex of the child (xx is female, xy is male)
mechanisms of heredity: deoxyribonucleic acid (DNA)
this is a molecular compound of four nucleotide bases that is the biochemical basis of heredity
- the four bases are: adenine, thymine, guanine, and cytosine
- thymine can only bond with adenine
- guanine can only bond with cytosine
mechanisms of heredity: gene
group of nuceotide bases that provide a set of biochemical instructions
mechanisms of heredity: genotype
person’s hereditary makeup
mechanisms of heredity: phenotype
physical, behavioural, and psychological features that result from the interaction between one’s genes and the environment
mechanisms of heredity: alleles
variations of genes
mechanisms of heredity: homozygous
when the alleles in a pair of chromosomes are the same
mechanisms of heredity: heterozygous
when the alleles in a pair of chromosomes are different (one can mask the other)
mechanisms of heredity: dominant gene
form of an allele whose chemical instructions are followed
mechanisms of heredity: recessive gene
allele whose instructions are ignored when it is combined with a dominant allele
-when this happens it is called dominant-recessive inheritance, or single-gene inheritance
mechanisms of heredity: incomplete dominance
this is a situation where one allele does not dominate the other completely, this is the cause of traits like sickle-cell trait
mechanisms of heredity: sickle cell trait
this is a dissorder where individuals show signs of mild anemia when they are deprived of oxygen (occurs in individuals who have one dominant allele for normal blood cells and one recessive sickle-cell allele)
genetic dissorders
- these can be inherited: where a child inherits a gene for a dissorder from one or both parents
- or they can involve more or fewer chromosomes, as can happen when parents eggs or sperm do not form properly
inherited disorders: phenylketonuria (PKU)
this is when the infant lacks a liver enzyme
- affects the ability to break down the phenylalanine, which if accumulated, can be a neurotoxic
- this is a recessive trait
inherited disorders: huntingtons disease
a progressive and fatal type of dementia
-this is a dominant trait, which is rare of serious dissorders
abnormal chromosomes: down syndrome (trisomy 21)
this is the most common chromosomal dissorder
- this person would have unusual charictaristics, impared cognitive development, and a shortened life expectancy
- they have an extra 21st chromosome, often provided by the egg
abnormal chromosomes: problems with autosomes and sex chromosomes
- when there is a problem with the autosomes it is typically very damaging, and often result in spontaneous abortion
- if there is a problem with the sex chromosomes there are also problems, however they would be less severe (unless you are missing the x chromosome, which the baby would die before birth)
abnormal chromosomes: problems with sex chromosomes: klinefelters syndrome
XXY would look like:
- tall
- male
- small balls
- sterile
- below-normal intelegence
- passive
XYY would loook like:
the same, but no small balls, not sterile, and not passive
abnormal chromosomes: problems with sex chromosomes: turners syndrome
X
this is a female, short, limited development of secondary sex charictaristics, problems perceiving spatial relations
abnormal chromosomes: problems with sex chromosomes: XXX syndrome
XXX
this is a female, normal stature, delayed motor and language development
mechanisms of heredity: chromosomes
threadlike structures in the nuclei of cells that contain genetic material
-each sperm and egg contains 23 chromosomes, giving the new organism 23 pairs (46)
heredity, envitonment and development
although certain aspects of heredity can greatly influence development, phenotypes are also under the influence of hte environment
behaviour genetics:
this is the branch of genetics that studies the inheritence of behavioural and psycholoical traits
- most human traits vary as a matter of degree rather than catagory
behaviour genetics: polygenic inheritance
when phenotypes are the result of the combined activity of many seperate genes
-most of these traits fall into a normal distribution (so it is likely that you will get a mix as opposed to something on either end)
monozygotic twins
this is the result of when a single fertilized egg splits to form two new individuals (identical twins)
dizygotic twins
this is the result of the fertilization of 2 seperate eggs by two sperm (fraternal twins)
twins: the difference between the two kinds
monozygotic twins have 100% genetic overlap and dizygotic twins do not
how to study adopted children
adoption studies involve comparing adopted children to:
- parents, both biological and adoptive
- siblings, both biological and adoptive
paths from genes to behaviour: some general principles
- heredity and environment interact dynamically throughout development
- genes can influence the kind of environment to which a person is exposed
- environmental influences tipically make children within a family different
from genes to behaviour: reaction range
this is when a genotype is manifested in reaction to the environment where development takes place so a single genotype can lead to a range of phenotypes
from genes to behaviour: niche-picking
this is when someone specifically picks out an environment that works with their genetic makeup
from genes to behaviour: non-shared environmental influences
these are the forces in a family that make siblings different from one another
from conception to birth: prenatal development, and the 3 stages
this is the many changes that happen to change a fertilized egg into a newborn human -this takes about 38 weeks three stages: -period of the zygote (weeks 1-2) -period of the embryo (weeks 3-8) -period of the fetus (weeks 9-38)
from conception to birth: period of the zygote (and define zygote)
weeks 1-2
zygote: fertilized egg
- during the first week after fertilization, travels down the fallopian tube toward the uterus
- spends the second week in the process of implantation (this is where the zygote burrows into the uterine wall and establishes connections with a woman’s blood vessels)
from conception to birth: period of the zygote: germ disc
this is the small cluster of cells near the centre of the zygote that will eventually develop into a baby
from conception to birth: period of the zygote: placenta
structure through which nutrients and wastes are exchanged between the mother and the developing child (this is formed from the layer of hte zygote’s cells that is closest to the uterus)
from conception to birth: period of the embryo: embryo
term given to the zygote once it is completely embedded in the uterine wall
from conception to birth: period of the embryo: what happens
weeks 3-8
three layers form in this time:
-ectoderm: this is the outer layer of the embryo that will become the hair, skin, and the nervous system
-mesoderm: middle layer of the embryo, becomes the muscles, bones, and circulatory system
-endoderm: inner layer of the embryo, which will become the lungs and the digestive system
from conception to birth: period of the embryo: what the embryo is supported by
amnion: inner sac where the developign child rests
amniotic fluid: surrounds the embryo or fetus
umbilical cord: contains veins and arteries that connects the developing child to the placenta
from conception to birth: period of the embryo: cephalocaudal principle
sequence of growth that occurs from the head down (head to caudal/tail region)