heredity and development across the lifespan Flashcards
what are genes
segments of DNA that code for a trait
what are alleles
paired maternal and paternal genes
what are chromosomes
strands of DNA
what are homologous chromosomes
maternal and paternal paired chromosomes
what is heterozygous
when alleles code for different expressions of a trait- one is dominant and the other is recessive
what are homozygous
when alleles code for the same expression of a trait
what are dominant alleles
an allele that if present, will be expressed. dominant alleles mask the expression of recessive alleles and are designated in capital letters
what are recessive alleles
alleles whose expression only occurs if there are 2 recessive alleles paired. recessive alleles are designated by lowercase letters
what is the genotype
genetic code of alleles for a trait
what is the phenotype
physical expression of a trait. what the person look like
how does independent assortment result in genetic variation
because of the random alignment and separation of chromosomes during meiosis which leads to four different daughter cells
how does crossing over result in genetic variation
because during crossing over, part of one maternal chromosomes DNA is exchanged with part of the father chromosome. this results in a hybrid chromosome with a unique pattern of genetic material.
how does random fertilization lead to genetic variation
When male and female gamete meet each other, each is the result of a number of genetic possibilities created during independent assortment and crossing over. Fertilization occurs between a random sperm and a random oocyte
what is simple inheritance
a single gene pair that codes for a particular trait (out of all 23 chromosomes only one holds the alleles for that trait)
what is complex inheritance
multiple gene pairs code for a particular trait.
dominant- recessive inheritance (simple inheritance)
there is a dominant gene code and a recessive gene code.
Dominant alleles are always expressed if present and recessive alleles are only expressed if they exist in homozygous pairs.
incomplete inheritance (simple inheritance)
it is a heterozygous genotype (one dominant and one recessive allele) that expresses an intermediate phenotype. it is rare
multiple allele inheritance and co-dominance (simple inheritance)
While an individual only inherits two alleles for each gene, some genes have more than two allele forms. Where a gene has more than two allele forms, the inheritance of those alleles is referred to as multiple-allele inheritance. And where two or more of the possible alleles are dominant, then co-dominance can occur. e.g ABO blood group- both A and B are dominant and are shown when together
sex-linked inheritance (simple inheritance)
genes that are on the sex chromosomes, also called the X and Y chromosomes. these chromosomes are not homologous as the X chromosome is much larger than the Y and therefore carries more genes. Females have two X chromosomes and therefore all genes are paired. males have one X and one Y chromosome and therefore the X will have a number of genes that are not paired. any gene on the X chromosome that does not have a match on the Y chromosome will be expressed even if recessive.
what are the three primary germ layers and what do they develop
- ectoderm- nervous system, bones of the cranium, epidermis
- mesoderm- everything else in the body
- endoderm- mucous membranes of the GI, respiratory tract, lower urogenital tract, associated glands
what factors influence gene expression
- other genes- some genes can influence the expression of other genes (turn off or on the other gene)
- other cellular genetic material;
- RNA- only genes
- histone proteins
- epigenetic marks
- mitochondrial DNA - environmental factors such as the environment, diet, illness, sun exposure, drugs etc
early human development of the embryo and foetus
- sperm comes into the oocyte and chromosomes join
- single cell zygote forms
- cleavage/ cell division into more cells creating a whole lot of replicated cells
- morula (ball of cells) is formed
- blastocyst with fluid filled space is formed. daughter cells form an outer layer and an inner cluster (the inner cluster forms the baby) that implants into the uterus.
- of the cluster in the blastocyte. one layer will form the amnion and the other forms the yolk
- another layer forms in the middle called primary germ layer. every structure in the human body develops from these 3 layers
key aspects of growth and development of infants and children
- motor development of the body tends to occur in a head-to-toe direction. babies learn to control movements of their eyes, then head, then trunk and upper then lower limbs
- growth and development happens in spurts
- period of most overall growth and development
growth in adolescence
- onset of puberty
- sexual maturity
- increase in sex hormones
- increase growth in height and weight
- increase in muscular and fat tissue
- increase in blood volume with increase in RBCs and iron
- appearance of secondary sex characteristics
- bony ossification completes
- significant neurological development
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what hormone increases during puberty
gonadal hormones
the rise in hormones of the HPG axis results in what for males
it promotes the start of spermatogenesis and maturation of the reproductive structures. males typically experience their first ejaculation during puberty
the rise in hormones of the HPG axis results in what for females
the ovarian cycle begins with the restart of meiosis 2 and follicular development, then the first period occurs initiating the first full uterine cycle.
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what are biological changes in adulthood and ageing
- accumulation of cellular debris both inside and outside of cells
- decrease in cellular function
what are physical and physiological effects of ageing
- skin loses its elasticity and becomes more delicate
- bone mass decreases and cartilage joints becomes worn away
- muscle lose tone, strength and flexibility
blood vessels stiffen - reaction time is slowed
- viability, and therefore fertility of gametes in both genders declines and females undergo menopause
