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Terms in this set (53)
nature refers to
contribution of genetics to one's development
specific sequence of nucleotides and are recipes for making proteins
estimated ___ genes for humans
normal human cells contain how many chromosomes? Where are chromosomes located?
-46 (23 from each parent)
most cells of the body are created by a process called...
the cell's nucleus making an exact copy of all the chromosomes and splitting into two new cells
-used in sexual reproduction
-the gamete's chromosomes duplicate, and then divide twice resulting in four cells containing only half the genetic material of the original gamete
cells used in sexual reproduction, called the gametes (sperm or ova), are formed in a process called
of the 23 pairs, 22 are similar in length
determination of male or female
If a child receives the combination of XY the child will be genetically male. If the child receives the combination XX the child will be genetically female.
refers to the sum total of all the genes a person inherits
refers to the features that are actually expressed
An organism that has two identical alleles for a trait
An organism that has two different alleles for a trait
-express themselves in the phenotype even when paired with a different version of the gene
-examples: facial dimples, curly hair, normal vision, and dark hair
-express themselves only when paired with a similar version gene
-examples: red hair, being nearsighted, and straight hair
different version of a gene
characteristic is the result of several genes
-the dominant gene does not completely suppress the recessive gene
-example: sickle cell anemia. this is a recessive gene disorder
Those who have inherited only one recessive-gene. Should be unaffected by recessive traits
describes identical twins. occurs when a fertilized egg splits apart in the first two weeks of development
two eggs or ova are released and fertilized by two separate sperm. produces fraternal twins
most known genetic disorders are... but most are not seriously debilitating
some disorders are sex-linked;
-the defective gene is found on the X-chromosome
-males are at greater risk bc they only have one X chromosome
-great risk of disorder due to recessive gene
-females would need to have recessive genes on both X chromosomes to be at risk
Genetic Disorders chart
occurs when a child inherits too many or two few chromosomes
sex-linked chromosomal abnormality
abnormality is on 23rd pair
-occurs when part or all of one of the X chromosomes is lost and the resulting zygote has an XO composition.
-occurs in 1 of every 2,500 live female births
-short stature and other physical characteristics
Klinefelter syndrome (XXY)
A service that assists individuals identify, test for, and explain potential genetic conditions that could adversely affect themselves or their offspring
common reasons for genetic counseling
-Family history of a genetic condition
-Membership in a certain ethnic group with a higher risk of a genetic condition -Information regarding the results of genetic testing, including blood tests, amniocentesis, or ultra sounds 41
-Learning about the chances of having a baby with a genetic condition if the parents are older, have had several miscarriages, have offspring with birth defects, experience infertility, or have a medical condition
-the scientific study of the interplay between the genetic and environmental contributions to behavior
-often referred to as nature v nurture
-refer to the processes by which genetic factors contribute to variations in the environment
Passive genotype-environment correlation
-occurs when children passively inherit the genes and the environments their family provides.
-examples: being genetically gifted in sports and having family encouragement
Evocative genotype-environment correlation
-refers to how the social environment reacts to individuals based on their inherited characteristics
-if a person is shy it will affect how they are treated by others
Active genotype-environment correlation
-occurs when individuals seek out environments that support their genetic tendencies
-when a child who is musically inclined seeks out music instruction/opportunities that facilitate their natural ability
-involve genetic susceptibility to the environment
-see pg 42 for adoption study
-studies modifications in DNA that affect gene expression and are passed on when the cells divide
-environmental factors: nutrition, stress, and teratogens are thought to change gene expression by switching genes on and off
-These gene changes can then be inherited by daughter cells. This would explain why monozygotic or identical twins may increasingly differ in gene expression with age
The germinal period
-about 14 days in length
-lasts from conception to implantation of the fertilized egg in the lining of the uterus
-sperm reaches egg, then wall hardens. tail of sperm falls off. head unites with nucleus of egg.
-fertilization typically occurs in fallopian tube then journeys to uterus
-newly formed cell after conception
-contains the combined genetic information from both parents
-consists of both an inner and outer group of cells
-embryonic disk: inner. will become the embryo
-trophoblast: outer. becomes the support system which nourishes the developing organism
-50-70% of blastocysts do not implant in uterine wall
after five days of mitosis, there are 100 cells which are now called...
during mitosis, fewer than ___ of all zygotes survive beyond the first two weeks. Why?
-the egg and sperm do not join properly, thus their genetic material does not combine, there is too little or damaged genetic material, the zygote does not replicate, or the blastocyst does not implant into the uterine wall
-Third week the blastocyst has implanted in the uterine wall.
-Upon implantation this multi-cellular organism is called an embryo.
-blood vessels grow forming the placenta. The placenta is a structure connected to the uterus that provides nourishment and oxygen from the mother to the developing embryo via the umbilical cord.
-During this period, cells continue to differentiate.
-Growth during prenatal development occurs in two major directions: from head to tail called cephalocaudal development and from the midline outward referred to as proximodistal development. This means that those structures nearest the head develop before those nearest the feet and those structures nearest the torso develop before those away from the center of the body
-in this stage, fetus has gills and a tail
-embryo can respond to touch and also move at this stage
why do some organisms fail during embryonic period?
usually due to gross chromosomal abnormalities
why is the embryo at so much risk during the embryonic period?
major structures are forming, mother might not know shes pregnant, at risk of consuming harmful substances in this stage
-9th week to birth
-by third month, fetus has developed all body parts including external genitalia
-In the following weeks, the fetus will develop hair, nails, teeth and the excretory and digestive systems will continue to develop. The fetus is about 3 inches long and weighs about 28 grams
during 4 to 6 months
the eyes become more sensitive to light and hearing develops. The respiratory system continues to develop, and reflexes such as sucking, swallowing and hiccupping, develop during the 5th month. Cycles of sleep and wakefulness are present at this time as well. The first chance of survival outside the womb, known as the age of viability is reached at about 24 weeks. Many practitioners hesitate to resuscitate before 24 weeks. The majority of the neurons in the brain have developed by 24 weeks, although they are still rudimentary, and the glial or nurse cells that support neurons continue to grow. At 24 weeks the fetus can feel pain
the fetus is primarily preparing for birth. It is exercising its muscles and its lungs begin to expand and contract. The fetus gains about 5 pounds and 7 inches during this last trimester of pregnancy, and during the 8th month a layer of fat develops under the skin. This layer of fat serves as insulation and helps the baby regulate body temperature after birth. At around 36 weeks the fetus is almost ready for birth. It weighs about 6 pounds and is about 18.5 inches long. By week 37 all of the fetus's organ systems are developed enough that it could survive outside the mother's uterus without many of the risks associated with premature birth. The fetus continues to gain weight and grow in length until approximately 40 weeks. By then the fetus has very little room to move around and birth becomes imminent.
The location of stem cells in the embryo
Prenatal Brain Development
-begins in third gestational week
-due to differentiation of stem cells
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