Textbook Notes (363,559)
Canada (158,426)
Psychology (9,578)
PSYB32H3 (1,174)
Chapter 2

PSYB20Fall2013 Chapter 2.docx

8 Pages
Unlock Document

University of Toronto Scarborough
Diane Mangalindan

PSYB20Fall2013 Chapter 2: Heredity and the Environment o Genotype  set of genes person inherits from their parents o Phenotype  interaction between genetic makeup and environment = the visible expression of the persons particular physical and behavioural characteristics Chromosomes and Genes o Humans = 23 pairs of chromosomes o Chromosome  thread like structure located in the nucleus of a cell that carry genetic information to help direct development o Meiosis  the process by which a germ cell divides to produce new germ cells with only HALF the normal complement of chromosomes  male and female germ cells each contain 23 chromosomes so that when they unite the new cell contains 46 chromosomes (half from each parent) o Crossing over  the process by which ewuibalent sections of homologous chromosomes switch places randomly shuffling genetic information each carries o Mitosis occurs in all autosomes and form the organism (baby) o Mitosis  process in which a body cell divides in 2, first duplicating its chromosomes so that the new daughter cells contain the usual 46 chromosomes o Autosomes  the 22 paired non-sex chrosmosomes THE PROCESS OF GENETIC TRANSMISSION o Ovum – egg  90 000x heavier than the sperm that penetrates it o They form the zygote in the oviduct o After 9 months, 7-8 lbs baby is born that is roughly 50cm in length Genes, DNA, and Proteins o Deoxyribonucleic acid (DNA)  ladder like molecule that stores genetic information in cells and transmits it during reproduction o DNA is made up of nucleotides o Nucleotide  compound containing N base, P group and sugar o Gene  a portion of DNA that is located at a particular site on a chromosome and that codes for the production of certain kinds of proteins o Proteins  fundamental components of living cells, and are any of a group of complex organic molecules containing carbon, hydrogen, oxygen, nitrogen and usually sulphur and that are composed of one or more chains of amino acids The Transmission of Traits: A Basic Model o Mendel’s 2 principles o Principle of segregation  each inherited trait comes from one’s parent as a separate unit o Principle of independent assortment  inheritance of different traits occurs independently of one another o Allele  alternative form of a gene o Homozygous  describing state of an individual whose alleles for a particular trait are the same o Heterozygous  describing state of an individual whose alleles for a particular trait from each parent differ o Co-dominance  genetic pattern in which heterozygous alleles express the variants of the trait for which they code simultaneously and with equal force o Dominant  more powerful of the 2 alleles in a heterozygous combo o Recessive  weaker of the 2 alleles in a heterozygous combination 1 GENETIC INFLUENCES ON DEVELOPMENT Genes on the Sex Chromosomes: Exceptions to the Rule rd o Sex chromosomes  the 23 pair of chromosomes which determine the individual’s gender are responsible for sex-related characteristics (XX in girls, XY in boys) o X-linked genes  genes that are carried on the X chromosomes and that may have no analogous genes on the Y chromosomes in males o Hemophilia  disorder caused by an X-linked recessive gene in which the blood fails to clot (found more often in males than females) o 120 males are conceived for every 100 females, and 106 males are born for every 100 females  but this numerical imbalance is rapidly eliminated over the course of development since males are more prone to X-linked disorders/diseases/anomalies than females so less reach sexual maturation and are able to reproduce Interactions among Genes o most characteristics are influenced by the interaction of many genes o modifier genes  genes that exert their influence indirectly by affecting the expression of still other genes Genetic Disorders o o 2 o o WHY HARMFUL ALLELES SURVIVE o because they are not harmful in the heterozygous state o example: Phenylketonuria  caused by recessive allele that fails to produce an enzyme necessary for the breakdown of phenyalanine, damages the nervous sytem and causes mental retardation 3 o 1 in 20 European descendants are heterozygous for PKU but have no symptoms o problems only arise when the zygote carries 2 recessive PKU alleles o so the harmful allele survives from generation to generation o some harmful alleles may survive because they are beneficial in combination with a normal allele o example of this is sickle cell anemia  homozygous recessive zygote develops this disease o heterozygous people for sickle cell anemia barely have any sickle RBC, unless they are exposed to low oxygen (for ex. At high altitudes) so they usually do not suffer from the harmful allele o in places around the world where prevalence of sickle cell anemia (heterozygosity) is high is also the same place where malaria is very prevalent o when parasite takes up residence in RBC, the RBC of heterozygous person sickle  the spleen then takes these sickled RBCs out of the system, with them also taking out the parasite o so people that are heterozygous for sickle cell anemia have built-in resistance to malaria  enourmous aid to survival since they live longer and hence reproduce more, so the ‘harmful’ gene is passed on CHROMOSOMAL ABNORMALITIES DOWN SYNDROME o a form of chromosome abnormality in which person suffers physical and mental development and is highly susceptible to such illnesses as leukemia, heart disorders and respiratory infections o characteristics: short, almond shaped eyes, moderate to severe mental retardation o 70% of people now live into their 60s but they are at a greater risk for developing Alzheimer’s disease later in life than the average person o trisomy 21  3 chromosomes 21  usually comes from mother’s egg by failure of separation during meiosis o this occurs more often when women are older o father’s age matters too  rates higher for men over 40, especially if mom is also over 35 o they are slow to learn to speak and have trouble attending to, discriminating and interpreting complex or subtle information from their environments  problems in communication between child and caregiver o children with DS can become competent adults who hold jobs and live independently in group homes SEX-CHROMOSOMAL ANOMALIES o Turner Syndrome  girl with XO pattern usually because father’s sperm contained neither an X nor a Y chromosome o Characteristics: short, stubby fingers, webbed necks, unusually shaped mouths and ears, normal intelligence by some deficits in visual and spatial processing and arithmetic reasoning o They do not develop female characterstics unless given hormones o They have difficulty discriminating and interpreting emotional cues and facial expressions in other so they have problems in social relationships o Women can also inherit and extra X XXX, cognitive abilities are affects, especially short term memory and verbal skills o Klinefelter’s Syndrome  XXY (boy), he is sterile and has many female characteristics, verbal language deficits and reading problems, memory and reasoning problems o Men can also inherit extra Y  XYY (usually taller than normal men) o Fragile X syndrome  more frequent in males than females o Characteristics: physical abnormalities, psychological and social problems (anxiety, hyperactivity, ADD, abnormal communication patterns) o Males may have deficits in social interactions and females may be more likely to suffer from depression and also to show cognitive and linguistic deficits 4 GENETIC COUNSELLING AND GENETIC ENGINEERING o Genetic counseling allows for at risk couples to make important decisions about getting pregnant, their risk of passing on a certain disease, or even screening during pregnancy, and caring for a child with a chromosomal abnormality o Genetic engineering allows for in vitro fertilization and allows for sterile males and females to have children with the aid of donor sperm or egg, and even surrogate mothers Prenatal Diagnostic Techniques COMMONLY USED TESTS o Amniocentesis  technique for sampling and assessing fetal cells for indications of abnormalities in the delveoping fetus, performed by inserting a needle through the abdominal wall and into the amniotic sac and withdrawing a small amount of the amniotic fluid o Performed at 16 weeks (enough cells in the amniotic fluid) but there is a 1 in 200-300 chance of miscarriage o Chorionic villi sampling  sampling and assessing cells withdrawn from the chorionic villi, which are projections from the chorion that surrounds the amniotic sac; cells are withdrawn either through a tube inserted into the uterus through the vagina or through a needle inserted through the abdominal wall o Chorionic villi sampling can be done earlier than amniocentesis (9-10 weeks) but is riskier o Huntington disease  found marker on chromosome 4 which made it possible to develop a test for Huntington gene o HD  fatal disorder of the nervous system that begins in mid adulthood and is manifested chiefly in uncontrollable, spasmodic movements of the body and limbs and eventual mental deterioration o 2 other prenatal tests are done routinely for most pregnancies o
More Less

Related notes for PSYB32H3

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.